Tagged: Qubits Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 7:21 pm on July 5, 2018 Permalink | Reply
    Tags: Able to process 10 billion photonic qubits every second, , Photons have added appeal because they can swiftly shuttle information over long distances and they are compatible with fabricated chips, , , Qubits, Semiconductor quantum transistor opens the door for photon-based computing   

    From Joint Quantum Institute: “Semiconductor quantum transistor opens the door for photon-based computing” 

    JQI bloc

    From Joint Quantum Institute

    1
    Researchers demonstrate the first single-photon transistor using a semiconductor chip. They used a single photon, stored in a quantum memory, to toggle the state of other photons. (Credit: E. Edwards/JQI)

    Transistors are tiny switches that form the bedrock of modern computing—billions of them route electrical signals around inside a smartphone, for instance.

    Quantum computers will need analogous hardware to manipulate quantum information. But the design constraints for this new technology are stringent, and today’s most advanced processors can’t be repurposed as quantum devices. That’s because quantum information carriers, dubbed qubits, have to follow different rules laid out by quantum physics.

    Scientists can use many kinds of quantum particles as qubits, even the photons that make up light. Photons have added appeal because they can swiftly shuttle information over long distances and they are compatible with fabricated chips. However, making a quantum transistor triggered by light has been challenging because it requires that the photons interact with each other, something that doesn’t ordinarily happen on its own.

    Now, researchers at the Joint Quantum Institute (JQI), led by JQI Fellow Edo Waks have cleared this hurdle and demonstrated the first single-photon transistor using a semiconductor chip. The device, described in the July 6 issue of Science , is compact: Roughly one million of these new transistors could fit inside a single grain of salt. It is also fast, able to process 10 billion photonic qubits every second.

    “Using our transistor, we should be able to perform quantum gates between photons,” says Waks. “Software running on a quantum computer would use a series of such operations to attain exponential speedup for certain computational problems.

    The photonic chip is made from a semiconductor with numerous holes in it, making it appear much like a honeycomb. Light entering the chip bounces around and gets trapped by the hole pattern; a small crystal called a quantum dot sits inside the area where the light intensity is strongest. Analogous to conventional computer memory, the dot stores information about photons as they enter the device. The dot can effectively tap into that memory to mediate photon interactions—meaning that the actions of one photon affect others that later arrive at the chip.

    “In a single-photon transistor the quantum dot memory must persist long enough to interact with each photonic qubit,” says Shuo Sun, the lead author of the new work who is a Postdoctoral Research Fellow at Stanford University*. “This allows a single photon to switch a bigger stream of photons, which is essential for our device to be considered a transistor.”

    To test that the chip operated like a transistor, the researchers examined how the device responded to weak light pulses that usually contained only one photon. In a normal environment, such dim light might barely register. However, in this device, a single photon gets trapped for a long time, registering its presence in the nearby dot.

    The team observed that a single photon could, by interacting with the dot, control the transmission of a second light pulse through the device. The first light pulse acts like a key, opening the door for the second photon to enter the chip. If the first pulse didn’t contain any photons, the dot blocked subsequent photons from getting through. This behavior is similar to a conventional transistor where a small voltage controls the passage of current through it’s terminals. Here, the researchers successfully replaced the voltage with a single photon and demonstrated that their quantum transistor could switch a light pulse containing around 30 photons before the quantum dot’s memory ran out.

    Waks, who is also a professor in the University of Maryland Department of Electrical and Computer Engineering, says that his team had to test different aspects of the device’s performance prior to getting the transistor to work. “Until now, we had the individual components necessary to make a single photon transistor, but here we combined all of the steps into a single chip,” Waks says.

    Sun says that with realistic engineering improvements their approach could allow many quantum light transistors to be linked together. The team hopes that such speedy, highly connected devices will eventually lead to compact quantum computers that process large numbers of photonic qubits.

    *Other contributors and affiliations

    Edo Waks has affiliations with the University of Maryland Department of Electrical and Computer Engineering (ECE), Department of Physics, Joint Quantum Institute, and the Institute for Research in Electronics and Applied Physics (IREAP).
    Shuo Sun was a UMD graduate student at the time of this research. He is now a postdoctoral research fellow at Stanford University.
    JQI Fellow Glenn Solomon, a physicist at the National Institute of Standards and Technology, grew the sample used in this research.
    Hyochul Kim was a postdoctoral research at UMD at the time of the research. He is now at Samsung Advanced Institute of Technology.
    Zhouchen Luo is currently a UMD ECE graduate student.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

    Advertisements
     
  • richardmitnick 11:17 am on May 23, 2018 Permalink | Reply
    Tags: A quantum internet promises completely secure communication, Engineering diamond strings that can be tuned to quiet a qubit’s environment and improve memory, John A Paulson School of Engineering and Applied Sciences at Harvard, , Qubits, Tunable diamond string may hold key to quantum memory, University of Cambridge   

    From John A Paulson School of Engineering and Applied Sciences: “Tunable diamond string may hold key to quantum memory” 

    Harvard School of Engineering and Applied Sciences
    From John A Paulson School of Engineering and Applied Sciences

    May 22, 2018

    Leah Burrows
    lburrows@seas.harvard.edu
    (617) 496-1351

    A process similar to guitar tuning improves storage time of quantum memory.

    1
    Electrodes stretch diamond strings to increase the frequency of atomic vibrations to which an electron is sensitive, just like tightening a guitar string increases the frequency or pitch of the string. The tension quiets a qubit’s environment and improves memory from tens to several hundred nanoseconds, enough time to do many operations on a quantum chip. (Second Bay Studios/Harvard SEAS)

    A quantum internet promises completely secure communication. But using quantum bits or qubits to carry information requires a radically new piece of hardware – a quantum memory. This atomic-scale device needs to store quantum information and convert it into light to transmit across the network.

    A major challenge to this vision is that qubits are extremely sensitive to their environment, even the vibrations of nearby atoms can disrupt their ability to remember information. So far, researchers have relied on extremely low temperatures to quiet vibrations but, achieving those temperatures for large-scale quantum networks is prohibitively expensive.

    Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the University of Cambridge have developed a quantum memory solution that is as simple as tuning a guitar.

    The researchers engineered diamond strings that can be tuned to quiet a qubit’s environment and improve memory from tens to several hundred nanoseconds, enough time to do many operations on a quantum chip.

    “Impurities in diamond have emerged as promising nodes for quantum networks,” said Marko Loncar, the Tiantsai Lin Professor of Electrical Engineering at SEAS and senior author of the research. “However, they are not perfect. Some kinds of impurities are really good at retaining information but have a hard time communicating, while others are really good communicators but suffer from memory loss. In this work, we took the latter kind, and improved the memory by ten times.”

    The research is published in Nature Communications.

    Impurities in diamond, known as silicon-vacancy color centers, are powerful qubits. An electron trapped in the center acts as a memory bit and can emit single photons of red light, which would in turn act as long-distance information carriers of a quantum internet. But with the nearby atoms in the diamond crystal vibrating randomly, the electron in the center quickly forgets any quantum information it is asked to remember.

    “Being an electron in a color center is like trying to study at a loud marketplace,” said Srujan Meesala, a graduate student at SEAS and co-first author of the paper. “There is all this noise around you. If you want to remember anything, you need to either ask the crowds to stay quiet or find a way to focus over the noise. We did the latter.”

    To improve memory in a noisy environment, the researchers carved the diamond crystal housing the color center into a thin string, about one micron wide — a hundred times thinner than a strand of hair — and attached electrodes to either side. By applying a voltage, the diamond string stretches and increases the frequency of vibrations the electron is sensitive to, just like tightening a guitar string increases the frequency or pitch of the string.

    “By creating tension in the string, we increase the energy scale of vibrations that the electron is sensitive to, meaning it can now only feel very high energy vibrations,” said Meesala. “This process effectively turns the surrounding vibrations in the crystal to an irrelevant background hum, allowing the electron inside the vacancy to comfortably hold information for hundreds of nanoseconds, which can be a really long time on the quantum scale. A symphony of these tunable diamond strings could serve as the backbone of a future quantum internet.”

    Next, the researchers hope to extend the memory of the qubits to the millisecond, which would enable hundreds of thousands of operations and long-distance quantum communication.

    The Harvard Office of Technology Development has protected the intellectual property relating to this project and is exploring commercialization opportunities.

    The research was co-first authored by Young-Ik Sohn and Srujan Meesala from Marko Loncar’s group at Harvard, and Benjamin Pingault from Mete Atature’s group at the University of Cambridge. Researchers from Harvard SEAS, Harvard Physics, Sandia National Laboratories also contributed to the manuscript.

    The research was supported by the National Science Foundation-sponsored Center for Integrated Quantum Materials, Office of Naval Research Multidisciplinary University Research Initiative on Quantum Optomechanics, NSF Emerging Frontiers in Research and Innovation ACQUIRE, the University of Cambridge, the ERC Consolidator Grant PHOENICS, and the EPSRC Quantum Technology Hub NQIT.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.
    stem
    Stem Education Coalition

    Through research and scholarship, the Harvard School of Engineering and Applied Sciences (SEAS) will create collaborative bridges across Harvard and educate the next generation of global leaders. By harnessing the power of engineering and applied sciences we will address the greatest challenges facing our society.

    Specifically, that means that SEAS will provide to all Harvard College students an introduction to and familiarity with engineering and technology as this is essential knowledge in the 21st century.

    Moreover, our concentrators will be immersed in the liberal arts environment and be able to understand the societal context for their problem solving, capable of working seamlessly withothers, including those in the arts, the sciences, and the professional schools. They will focus on the fundamental engineering and applied science disciplines for the 21st century; as we will not teach legacy 20th century engineering disciplines.

    Instead, our curriculum will be rigorous but inviting to students, and be infused with active learning, interdisciplinary research, entrepreneurship and engineering design experiences. For our concentrators and graduate students, we will educate “T-shaped” individuals – with depth in one discipline but capable of working seamlessly with others, including arts, humanities, natural science and social science.

    To address current and future societal challenges, knowledge from fundamental science, art, and the humanities must all be linked through the application of engineering principles with the professions of law, medicine, public policy, design and business practice.

    In other words, solving important issues requires a multidisciplinary approach.

    With the combined strengths of SEAS, the Faculty of Arts and Sciences, and the professional schools, Harvard is ideally positioned to both broadly educate the next generation of leaders who understand the complexities of technology and society and to use its intellectual resources and innovative thinking to meet the challenges of the 21st century.

    Ultimately, we will provide to our graduates a rigorous quantitative liberal arts education that is an excellent launching point for any career and profession.

     
  • richardmitnick 1:31 pm on March 29, 2018 Permalink | Reply
    Tags: , Inelastic neutron scattering, Nanomagnets, , , , , Qubits, The possibility of producing qubits from organometallic molecules with a single magnetic ion in each molecule   

    From Niels Bohr Institute: “Neutron scattering brings us a step closer to the quantum computer” 

    Niels Bohr Institute bloc

    Niels Bohr Institute

    29 March 2018

    Mikkel Agerbæk Sørensen,
    Ph.D.-student, Department of Chemistry, University of Copenhagen
    mikkel.agerbaek@chem.ku.dk
    http://www.ki.ku.dk

    Ursula Bengård Hansen,
    Postdoc, X-ray and Neutron Science
    Niels Bohr Institute, University of Copenhagen
    uhansen@nbi.ku.dk
    +45 60 47 86 15

    Kim Lefmann,
    Lektor, X-ray and Neutron Science
    Niels Bohr Institute, University of Copenhagen
    lefmann@nbi.ku.dk
    +45 29 25 04 76

    Jesper Bendix,
    Professor, Kemisk Institut, University of Copenhagen
    bendix@kiku.dk
    +45 35 32 01 01

    Quantum computers:

    A major challenge for future quantum computers is that you have to keep the quantum information long enough to make calculations on it – but the information only has a very short lifespan, often less than a microsecond. Now researchers at the Niels Bohr Institute and the Department of Chemistry at the University of Copenhagen, in collaboration with a team of international researchers, have come closer to a solution. The results are published in the renowned journal Nature Communications.

    1
    PhD student Mikkel Agerbæk Sørensen from the Department of Chemistry and Postdoc Ursula Bengård Hansen from the research group X-ray and Neutron Science at the Niels Bohr Institute shows a 3D model of the studied molecule. By making small changes in the form of the molecule, the tunnelling can be suppressed. In the background Associate Professor Kim Lefmann and Professor Jesper Bendix. Photo: Ola J. Joensen.

    In order to build the quantum computer of the future, you need to be able to store the quantum information – what we call “quantum bits” or “qubits” – (which corresponds to bits and bytes in a traditional computer). Several research groups are experimenting with different ideas for how this can be done in practice.

    A team of chemists and physicists from the Niels Bohr Institute and the Department of Chemistry at the University of Copenhagen, as well as collaborators from Germany, France, Switzerland, Spain and the United States, have studied the possibility of producing qubits from organometallic molecules with a single magnetic ion in each molecule.

    In these “nanomagnets” there is the particular challenge that random movements in the outside world can interfere with the magnetic ions, so that the quantum information is lost before you can manage to perform calculations with it. Even at ultra-low temperatures just above absolute zero (0.05 Kelvin), where all motion “normally” stops, the system can still be subjected to quantum mechanical disturbances, also known as “tunnelling”.

    Mikkel Agerbæk Sørensen, who is the first author of the study, explains that suppressing the tunnelling is considered one of the greatest challenges in the production of new nanomagnets with actual application possibilities: “there are several theoretical models for how to suppress the tunnelling in such molecule-based magnets. With this study, we are the first to have been able to prove the leading model experimentally.”

    Changes in the form of the molecule are part of the solution

    There is still a long way to go to be able to use these nanomagnets in a practical quantum computer, but the researchers have now discovered another “control lever”, namely the geometric form of the molecule that can be used to get closer to the goal. With the construction of the largest neutron facility (ESS) in Lund, Sweden, researchers will have better opportunities to measure and understand tunnelling, thus getting closer to controlling it – and ultimately pave the way for quantum computing.

    3
    In order to understand the quantum behavior of a molecule-based magnet, it is necessary to measure the energy levels of the molecule very accurately. This is best done with the so-called inelastic neutron scattering. Such experiments can only be done using instruments located at major international research facilities. With the performance of ESS, researchers at the University of Copenhagen will have even better opportunities to conduct such studies. Here Mikkel Agerbæk Sørensen at the entrance of the instrument IN6 at the Institute Laue-Langevin in Grenoble.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Niels Bohr Institute Campus

    The Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

    The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

    During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

    On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

     
  • richardmitnick 4:14 pm on March 7, 2018 Permalink | Reply
    Tags: , , Qubits, ,   

    From University of New South Wales: “Seeing is believing – precision atom qubits achieve major milestone” 

    U NSW bloc

    University of New South Wales

    07 Mar 2018
    Deborah Smith

    The unique Australian approach of creating quantum bits from precisely positioned individual atoms in silicon is reaping major rewards, with two of these atom qubits made to “talk” to each other for the first time.

    1
    Scientia Professor Michelle Simmons with a scanning tunnelling microscope. Credit: UNSW

    The unique Australian approach of creating quantum bits from precisely positioned individual atoms in silicon is reaping major rewards, with UNSW Sydney-led scientists showing for the first time that they can make two of these atom qubits “talk” to each other.

    The team – led by UNSW Scientia Professor Michelle Simmons, Director of the Centre of Excellence for Quantum Computation and Communication Technology, or CQC2T – is the only group in the world that has the ability to see the exact position of their qubits in the solid state.

    Simmons’ team create the atom qubits by precisely positioning and encapsulating individual phosphorus atoms within a silicon chip. Information is stored on the quantum spin of a single phosphorus electron.

    The team’s latest advance – the first observation of controllable interactions between two of these qubits – is published in the journal Nature Communications. It follows two other recent breakthroughs using this unique approach to building a quantum computer.

    By optimising their nano-manufacturing process, Simmons’ team has also recently created quantum circuitry with the lowest recorded electrical noise of any semiconductor device.

    And they have created an electron spin qubit with the longest lifetime ever reported in a nano-electric device – 30 seconds.

    “The combined results from these three research papers confirm the extremely promising prospects for building multi-qubit systems using our atom qubits,” says Simmons.

    2018 Australian of the Year inspired by Richard Feynman

    Simmons, who was named 2018 Australian of the Year in January for her pioneering quantum computing research, says her team’s ground-breaking work is inspired by the late physicist Richard Feynman.

    “Feynman said: ‘What I cannot create, I do not understand’. We are enacting that strategy systematically, from the ground up, atom by atom,” says Simmons.

    “In placing our phosphorus atoms in the silicon to make a qubit, we have demonstrated that we can use a scanning probe to directly measure the atom’s wave function, which tells us its exact physical location in the chip. We are the only group in the world who can actually see where our qubits are.

    “Our competitive advantage is that we can put our high-quality qubit where we want it in the chip, see what we’ve made, and then measure how it behaves. We can add another qubit nearby and see how the two wave functions interact. And then we can start to generate replicas of the devices we have created,” she says.

    2
    A scanning tunnelling microscope image showing the electron wave function of a qubit made from a phosphorus atom precisely positioned in silicon. Credit: UNSW

    For the new study, the team placed two qubits – one made of two phosphorus atoms and one made of a single phosphorus atom – 16 nanometres apart in a silicon chip.

    “Using electrodes that were patterned onto the chip with similar precision techniques, we were able to control the interactions between these two neighbouring qubits, so the quantum spins of their electrons became correlated,” says study lead co-author, Dr Matthew Broome, formerly of UNSW and now at the University of Copenhagen.

    “It was fascinating to watch. When the spin of one electron is pointing up, the other points down, and vice versa.

    “This is a major milestone for the technology. These type of spin correlations are the precursor to the entangled states that are necessary for a quantum computer to function and carry out complex calculations,” he says.

    Study lead co-author, UNSW’s Sam Gorman, says: “Theory had predicted the two qubits would need to be placed 20 nanometres apart to see this correlation effect. But we found it occurs at only 16 nanometres apart.

    “In our quantum world, this is a very big difference,” he says. “It is also brilliant, as an experimentalist, to be challenging the theory.”


    UNSW Sydney-led scientists have shown for the first time that they can make two precisely placed phosphorous atom qubits “talk” to each other.

    Leading the race to build a quantum computer in silicon

    UNSW scientists and engineers at CQC2T are leading the world in the race to build a quantum computer in silicon. They are developing parallel patented approaches using single atom and quantum dot qubits.

    “Our hope is that both approaches will work well. That would be terrific for Australia,” says Simmons.

    The UNSW team have chosen to work in silicon because it is among the most stable and easily manufactured environments in which to host qubits, and its long history of use in the conventional computer industry means there is a vast body of knowledge about this material.

    In 2012, Simmons’ team, who use scanning tunnelling microscopes to position the individual phosphorus atoms in silicon and then molecular beam epitaxy to encapsulate them, created the world’s narrowest conducting wires, just four phosphorus atoms across and one atom high.

    In a recent paper published in the journal Nano Letters, they used similar atomic scale control techniques to produce circuitry about 2-10 nanometres wide and showed it had the lowest recorded electrical noise of any semiconductor circuitry. This work was undertaken jointly with Saquib Shamim and Arindam Ghosh of the Indian Institute of Science.

    “It’s widely accepted that electrical noise from the circuitry that controls the qubits will be a critical factor in limiting their performance,” says Simmons.

    “Our results confirm that silicon is an optimal choice, because its use avoids the problem most other devices face of having a mix of different materials, including dielectrics and surface metals, that can be the source of, and amplify, electrical noise.

    “With our precision approach we’ve achieved what we believe is the lowest electrical noise level possible for an electronic nano-device in silicon – three orders of magnitude lower than even using carbon nanotubes,” she says.

    In another recent paper in Science Advances, Simmons’ team showed their precision qubits in silicon could be engineered so the electron spin had a record lifetime of 30 seconds – up to 16 times longer than previously reported. The first author, Dr Thomas Watson, was at UNSW undertaking his PhD and is now at Delft University of Technology.

    “This is a hot topic of research,” says Simmons. “The lifetime of the electron spin – before it starts to decay, for example, from spin up to spin down – is vital. The longer the lifetime, the longer we can store information in its quantum state.”

    In the same paper, they showed that these long lifetimes allowed them to read out the electron spins of two qubits in sequence with an accuracy of 99.8 percent for each, which is the level required for practical error correction in a quantum processor.

    Australia’s first quantum computing company

    Instead of performing calculations one after another, like a conventional computer, a quantum computer would work in parallel and be able to look at all the possible outcomes at the same time. It would be able to solve problems in minutes that would otherwise take thousands of years.

    Last year, Australia’s first quantum computing company – backed by a unique consortium of governments, industry and universities – was established to commercialise CQC2T’s world-leading research.

    Operating out of new laboratories at UNSW, Silicon Quantum Computing Pty Ltd has the target of producing a 10-qubit demonstration device in silicon by 2022, as the forerunner to a silicon-based quantum computer.

    The Australian government has invested $26 million in the $83 million venture through its National Innovation and Science Agenda, with an additional $25 million coming from UNSW, $14 million from the Commonwealth Bank of Australia, $10 million from Telstra and $8.7 million from the NSW Government.

    It is estimated that industries comprising approximately 40% of Australia’s current economy could be significantly impacted by quantum computing. Possible applications include software design, machine learning, scheduling and logistical planning, financial analysis, stock market modelling, software and hardware verification, climate modelling, rapid drug design and testing, and early disease detection and prevention.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    U NSW Campus

    Welcome to UNSW Australia (The University of New South Wales), one of Australia’s leading research and teaching universities. At UNSW, we take pride in the broad range and high quality of our teaching programs. Our teaching gains strength and currency from our research activities, strong industry links and our international nature; UNSW has a strong regional and global engagement.

    In developing new ideas and promoting lasting knowledge we are creating an academic environment where outstanding students and scholars from around the world can be inspired to excel in their programs of study and research. Partnerships with both local and global communities allow UNSW to share knowledge, debate and research outcomes. UNSW’s public events include concert performances, open days and public forums on issues such as the environment, healthcare and global politics. We encourage you to explore the UNSW website so you can find out more about what we do.

     
  • richardmitnick 3:10 pm on December 10, 2017 Permalink | Reply
    Tags: , , , Qubits   

    From IST Austria: “Essential quantum computer component downsized by two orders of magnitude” 

    Institute of Science and Technology Austria

    November 14, 2017

    Researchers at IST Austria have built compact photon directional devices. Their micrometer-scale, nonmagnetic devices route microwave photons and can shield qubits from harmful noise.

    1
    The new nonreciprocal device acts as a roundabout for photons.
    Here, arrows show the direction of photons propagation.
    Credit: IST Austria/Birgit Rieger

    Qubits, or quantum bits, are the key building blocks that lie at the heart of every quantum computer. In order to perform a computation, signals need to be directed to and from qubits. At the same time, these qubits are extremely sensitive to interference from their environment, and need to be shielded from unwanted signals, in particular from magnetic fields. It is thus a serious problem that the devices built to shield qubits from unwanted signals, known as nonreciprocal devices, are themselves producing magnetic fields. Moreover, they are several centimeters in size, which is problematic, given that a large number of such elements is required in each quantum processor. Now, scientists at the Institute of Science and Technology Austria (IST Austria), simultaneously with competing groups in Switzerland and the United States, have decreased the size of nonreciprocal devices by two orders of magnitude. Their device, whose function they compare to that of a traffic roundabout for photons, is only about a tenth of a millimeter in size, and—maybe even more importantly—it is not magnetic. Their study was published in the open access journal Nature Communications.

    When researchers want to receive a signal, for instance a microwave photon, from a qubit, but also prevent noise and other spurious signals from traveling back the same way towards the qubit, they use nonreciprocal devices, such as isolators or circulators. These devices control the signal traffic, similar to the way traffic is regulated in everyday life. But in the case of a quantum computer, it is not cars that cause the traffic but photons in transmission lines. “Imagine a roundabout in which you can only drive counterclockwise”, explains first author Dr. Shabir Barzanjeh, who is a postdoc in Professor Johannes Fink’s group at IST Austria. “At exit number one, at the bottom, there is our qubit. Its faint signal can go to exit number two at the top. But a signal coming in from exit number two cannot travel the same path back to the qubit. It is forced to travel in a counterclockwise manner, and before it reaches exit one, it encounters exit three. There, we block it and keep it from harming the qubit.”

    The ‘roundabouts’ the group has designed consist of aluminum circuits on a silicon chip and they are the first to be based on micromechanical oscillators: Two small silicon beams oscillate on the chip like the strings of a guitar and interact with the electrical circuit. These devices are tiny in size—only about a tenth of a millimeter in diameter—, one of the major advantages the new component has over its traditional predecessors, which were a few centimeters wide.

    Currently, only a few qubits have been used to test the principles of quantum computers, but in the future, thousands or even millions of qubits will be connected together, and many of these qubits will require their own circulator. “Imagine building a processor that has millions of such centimeter-size components. It would be enormous and impractical,” says Shabir Barzanjeh. “Using our nonmagnetic and very compact on-chip circulators instead makes life a lot easier.” Yet some hurdles need to be overcome before the devices will be used for this specific application. For example, the available signal bandwidth is currently still quite small, and the required drive powers might harm the qubits. However, the researchers are confident that these problems will turn out to be solvable.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The Institute of Science and Technology Austria (IST Austria) is a young international institute dedicated to basic research and graduate education in the natural and mathematical sciences, located in Klosterneuburg on the outskirts of Vienna. Established jointly by the federal government of Austria and the provincial government of Lower Austria, the Institute was inaugurated in 2009 and will grow to about 90 research groups by 2026.

    The governance and management structures of IST Austria guarantee its independence and freedom from political and commercial influences. The Institute is headed by the President, who is appointed by the Board of Trustees and advised by the Scientific Board. The first President of IST Austria is Thomas A. Henzinger, a leading computer scientist and former professor of the University of California at Berkeley and the EPFL Lausanne in Switzerland.

     
  • richardmitnick 10:31 am on December 10, 2017 Permalink | Reply
    Tags: , , , Qubits   

    From JQI: “Quantum simulators wield control over more than 50 qubits” 

    JQI bloc

    Joint Quantum Institute

    November 29, 2017 [Just appeared in social media.]
    E. Edwards

    Research Contact
    Christopher Monroe
    monroe@umd.edu

    Atoms provide a robust platform for observing quantum magnets in action.

    1
    Artist’s depiction of quantum simulation. Lasers manipulate an array of over 50 atomic qubits in order to study the dynamics of quantum magnetism (credit: E. Edwards/JQI).

    Two independent teams of scientists, including one from the Joint Quantum Institute, have used more than 50 interacting atomic qubits to mimic magnetic quantum matter, blowing past the complexity of previous demonstrations. The results appear in this week’s issue of Nature.

    As the basis for its quantum simulation, the JQI team deploys up to 53 individual ytterbium ions—charged atoms trapped in place by gold-coated and razor-sharp electrodes. A complementary design by Harvard and MIT researchers uses 51 uncharged rubidium atoms confined by an array of laser beams. With so many qubits these quantum simulators are on the cusp of exploring physics that is unreachable by even the fastest modern supercomputers. And adding even more qubits is just a matter of lassoing more atoms into the mix.

    “Each ion qubit is a stable atomic clock that can be perfectly replicated,” says JQI Fellow Christopher Monroe*, who is also the co-founder and chief scientist at the startup IonQ Inc. “They are effectively wired together with external laser beams. This means that the same device can be reprogrammed and reconfigured, from the outside, to adapt to any type of quantum simulation or future quantum computer application that comes up.” Monroe has been one of the early pioneers in quantum computing and his research group’s quantum simulator is part of a blueprint for a general-purpose quantum computer.

    Quantum hardware for a quantum problem

    While modern, transistor-driven computers are great for crunching their way through many problems, they can screech to a halt when dealing with more than 20 interacting quantum objects. That’s certainly the case for quantum magnetism, in which the interactions can lead to magnetic alignment or to a jumble of competing interests at the quantum scale.

    “What makes this problem hard is that each magnet interacts with all the other magnets,” says research scientist Zhexuan Gong, lead theorist and co-author on the study. “With the 53 interacting quantum magnets in this experiment, there are over a quadrillion possible magnet configurations, and this number doubles with each additional magnet. Simulating this large-scale problem on a conventional computer is extremely challenging, if at all possible.”

    When these calculations hit a wall, a quantum simulator may help scientists push the envelope on difficult problems. This is a restricted type of quantum computer that uses qubits to mimic complex quantum matter. Qubits are isolated and well-controlled quantum systems that can be in a combination of two or more states at once. Qubits come in different forms, and atoms—the versatile building blocks of everything—are one of the leading choices for making qubits. In recent years, scientists have controlled 10 to 20 atomic qubits in small-scale quantum simulations.

    Currently, tech industry behemoths, startups and university researchers are in a fierce race to build prototype quantum computers that can control even more qubits. But qubits are delicate and must stay isolated from the environment to protect the device’s quantum nature. With each added qubit this protection becomes more difficult, especially if qubits are not identical from the start, as is the case with fabricated circuits. This is one reason that atoms are an attractive choice that can dramatically simplify the process of scaling up to large-scale quantum machinery.

    An atomic advantage

    Unlike the integrated circuitry of modern computers, atomic qubits reside inside of a room-temperature vacuum chamber that maintains a pressure similar to outer space. This isolation is necessary to keep the destructive environment at bay, and it allows the scientists to precisely control the atomic qubits with a highly engineered network of lasers, lenses, mirrors, optical fibers and electrical circuitry.

    “The principles of quantum computing differ radically from those of conventional computing, so there’s no reason to expect that these two technologies will look anything alike,” says Monroe.

    In the 53-qubit simulator, the ion qubits are made from atoms that all have the same electrical charge and therefore repel one another. But as they push each other away, an electric field generated by a trap forces them back together. The two effects balance each other, and the ions line up single file. Physicists leverage the inherent repulsion to create deliberate ion-to-ion interactions, which are necessary for simulating of interacting quantum matter.

    The quantum simulation begins with a laser pulse that commands all the qubits into the same state. Then, a second set of laser beams interacts with the ion qubits, forcing them to act like tiny magnets, each having a north and south pole. The team does this second step suddenly, which jars the qubits into action. They feel torn between two choices, or phases, of quantum matter. As magnets, they can either align their poles with their neighbors to form a ferromagnet or point in random directions yielding no magnetization. The physicists can change the relative strengths of the laser beams and observe which phase wins out under different laser conditions.

    The entire simulation takes only a few milliseconds. By repeating the process many times and measuring the resulting states at different points during the simulation, the team can see the process as it unfolds from start to finish. The researchers observe how the qubit magnets organize as different phases form, dynamics that the authors say are nearly impossible to calculate using conventional means when there are so many interactions.

    This quantum simulator is suitable for probing magnetic matter and related problems. But other kinds of calculations may need a more general quantum computer with arbitrarily programmable interactions in order to get a boost.

    “Quantum simulations are widely believed to be one of the first useful applications of quantum computers,” says Alexey Gorshkov**, JQI Fellow and co-author of the study. “After perfecting these quantum simulators, we can then implement quantum circuits and eventually quantum-connect many such ion chains together to build a full-scale quantum computer with a much wider domain of applications.”

    As they look to add even more qubits, the team believes that its simulator will embark on more computationally challenging terrain, beyond magnetism. “We are continuing to refine our system, and we think that soon, we will be able to control 100 ion qubits, or more,” says Jiehang Zhang, the study’s lead author and postdoctoral researcher. “At that point, we can potentially explore difficult problems in quantum chemistry or materials design.”

    Written by E. Edwards

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

     
  • richardmitnick 10:07 am on July 13, 2017 Permalink | Reply
    Tags: , Electron valley states, , , , Qubits,   

    From UCLA: “Technique for measuring and controlling electron state is a breakthrough in quantum computing” 

    UCLA bloc

    UCLA

    July 06, 2017
    Meghan Steele Horan

    1
    UCLA professor HongWen Jiang (center) and graduate students Blake Freeman and Joshua Schoenfield affixing a quantum dot device to the gold plate of a cooling chamber. Nick Penthorn.

    During their research for a new paper on quantum computing, HongWen Jiang, a UCLA professor of physics, and Joshua Schoenfield, a graduate student in his lab, ran into a recurring problem: They were so excited about the progress they were making that when they logged in from home to their UCLA desktop — which allows only one user at a time — the two scientists repeatedly knocked each other off of the remote connection.

    The reason for their enthusiasm: Jiang and his team created a way to measure and control the energy differences of electron valley states in silicon quantum dots, which are a key component of quantum computing research. The technique could bring quantum computing one step closer to reality.

    “It’s so exciting,” said Jiang, a member of the California NanoSystems Institute. “We didn’t want to wait until the next day to find out the outcome.”

    Quantum computing could enable more complex information to be encoded on much smaller computer chips, and it holds promise for faster, more secure problem-solving and communications than today’s computers allow.

    In standard computers, the fundamental components are switches called bits, which use 0s and 1s to indicate that they are off or on. The building blocks of quantum computers, on the other hand, are quantum bits, or qubits.

    The UCLA researchers’ breakthrough was being able to measure and control a specific state of a silicon quantum dot, known as a valley state, an essential property of qubits. The research was published in Nature Communications.

    “An individual qubit can exist in a complex wave-like mixture of the state 0 and the state 1 at the same time,” said Schoenfield, the paper’s first author. “To solve problems, qubits must interfere with each other like ripples in a pond. So controlling every aspect of their wave-like nature is essential.”

    Silicon quantum dots are small, electrically confined regions of silicon, only tens of nanometers across, that can trap electrons. They’re being studied by Jiang’s lab — and by researchers around the world — for their possible use in quantum computing because they enable scientists to manipulate electrons’ spin and charge.

    Besides electrons’ spin and charge, another of their most important properties is their “valley state,” which specifies where an electron will settle in the non-flat energy landscape of silicon’s crystalline structure. The valley state represents a location in the electron’s momentum, as opposed to an actual physical location.

    Scientists have realized only recently that controlling valley states is critical for encoding and analyzing silicon-based qubits, because even the tiniest imperfections in a silicon crystal can alter valley energies in unpredictable ways.

    “Imagine standing on top of a mountain and looking down to your left and right, noticing that the valleys on either side appear to be the same but knowing that one valley was just 1 centimeter deeper than the other,” said Blake Freeman, a UCLA graduate student and co-author of the study. “In quantum physics, even that small of a difference is extremely important for our ability to control electrons’ spin and charge states.”

    At normal temperatures, electrons bounce around, making it difficult for them to rest in the lowest energy point in the valley. So to measure the tiny energy difference between two valley states, the UCLA researchers placed silicon quantum dots inside a cooling chamber at a temperature near absolute zero, which allowed the electrons to settle down. By shooting fast electrical pulses of voltage through them, the scientists were able to move single electrons in and out of the valleys. The tiny difference in energy between the valleys was determined by observing the speed of the electron’s rapid switching between valley states.

    After manipulating the electrons, the researchers ran a nanowire sensor very close to the electrons. Measuring the wire’s resistance allowed them to gauge the distance between an electron and the wire, which in turn enabled them to determine which valley the electron occupied.

    The technique also enabled the scientists, for the first time, to measure the extremely small energy difference between the two valleys — which had been impossible using any other existing method.

    In the future, the researchers hope to use more sophisticated voltage pulses and device designs to achieve full control over multiple interacting valley-based qubits.

    “The dream is to have an array of hundreds or thousands of qubits all working together to solve a difficult problem,” Schoenfield said. “This work is an important step toward realizing that dream.”

    The research was supported by the U.S. Army Research Office.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    UC LA Campus

    For nearly 100 years, UCLA has been a pioneer, persevering through impossibility, turning the futile into the attainable.

    We doubt the critics, reject the status quo and see opportunity in dissatisfaction. Our campus, faculty and students are driven by optimism. It is not naïve; it is essential. And it has fueled every accomplishment, allowing us to redefine what’s possible, time after time.

    This can-do perspective has brought us 12 Nobel Prizes, 12 Rhodes Scholarships, more NCAA titles than any university and more Olympic medals than most nations. Our faculty and alumni helped create the Internet and pioneered reverse osmosis. And more than 100 companies have been created based on technology developed at UCLA.

     
  • richardmitnick 8:59 am on June 29, 2017 Permalink | Reply
    Tags: A 100-dimensional quantum system from the entanglement of two subatomic particles, , , Multi-coloured photons in 100 dimensions may make quantum computers stronger, , Qubits, Qutrits   

    From COSMOS: “Multi-coloured photons in 100 dimensions may make quantum computers stronger” 

    Cosmos Magazine bloc

    COSMOS

    29 June 2017
    Andrew Masterson

    1
    An illustration showing high-dimensional color-entangled photon states from a photonic chip, manipulated and transmitted via telecommunications systems.
    Michael Kues.

    By using manipulating the frequency of entangled photons, researchers have found a way to make more stable tools for quantum computing from off-the-shelf equipment.

    Researchers using off-the-shelf telecommunications equipment have created a 100-dimensional quantum system from the entanglement of two subatomic particles.

    The system can be controlled and manipulated to perform high-level gateway functions – a critical component of any viable quantum computer – the scientists report in the journal Nature.

    The team, led by Michael Kues of the University of Glasgow, effectively created a quantum photon generator on a chip. The tiny device uses a micro-ring resonator generate entangled pairs of photons from a laser input.

    The entanglement is far from simple. Each photon is composed of a superposition of several different colours, all expressed simultaneously, giving the photon several dimensions. The expression of any individual colour – or frequency, if you like – is mirrored across the two entangled photons, regardless of the distance between them.

    The complexity of the photon pairs represents a major step forward in manipulating quantum entities.

    Almost all research into quantum states, for the purpose of developing quantum computing, has to date focussed on qubits: artificially created subatomic particles that exist in a superposition two possible states. (They are the quantum equivalent of standard computing ‘bits’, basic units that are capable only of being switched between 1 and 0, or yes/no, or on/off.)

    Kues and colleagues are instead working with qudits, which are essentially qubits with superpositions comprising three or more states.

    In 2016, Russian researchers showed that qudit-based quantum computing systems were inherently more stable than their two dimensional predecessors.

    The Russians, however, were working with a subset of qudits called qutrits, which comprise a superposition of three possible states. Kues and his team upped the ante considerably, fashioning qudits comprising 10 possible states – one for each of the colours, or frequencies, of the photon – giving an entangled pair a minimum of 100.

    And that’s just the beginning. Team member Roberto Morandotti of the University of Electronic Science and Technology of China, in Chengdu, suggests that further refinement will produce entangled two-qudit systems containing as many as 9000 dimensions, bringing a robustness and complexity to quantum computers that is at present unreachable.

    Kues adds that perhaps the most attractive feature of his team’s achievement is that it was done using commercially available components. This means that the strategy can be quickly and easily adapted by other researchers in the field, potentially ushering in a period of very rapid development.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 11:31 am on May 29, 2017 Permalink | Reply
    Tags: , , Doped diamond, , Qubits,   

    From COSMOS: “Doped diamond may lead to everyday quantum computers” 

    Cosmos Magazine bloc

    COSMOS

    29 May 2017
    Andrew Masterson

    1
    Precise placement of atoms in a diamond lattice may be a handy technique for quantum computer manufacture. Victor Habbick Visions / Getty

    Quantum computers are still halfway mythical, but they are moving closer to reality step by tiny step.

    One of the most widely favoured structures for building viable quantum computers is a diamond surface dotted with irregularities only a couple of atoms wide.

    The problem researchers face, however, is making sure those irregularities – essentially atom-scale holes and accompanying bits of atom-wide foreign material – are drilled into the diamond substrate in exactly the right spot.

    A report at Nature Communications by a team from MIT, Harvard University, and Sandia National Laboratories, in the US, covers a new method of doing so, creating the “defects” in the diamond crystal structure within 50 nanometres of their optimal locations.

    The precise placement of the irregularities – known as “dopant-vacancies” in the business – is a critical outcome if quantum computers are ever to end up on the market.

    This is because the combination of a tiny hole and a couple of atoms of non-diamond matter – nitrogen, for instance – can be engineered to act as a qubit, the fundamental element of quantum computing.

    At the heart of a qubit is a subatomic particle that can simultaneously occupy a number of contradictory states – on, off, and a “superposition” of both together, for instance. The combination of the hole, the foreign atoms, and the light refracted through the diamond combine to create an elegant qubit.

    At least, theoretically. To date, most experimental work has been done using nitrogen dopant-vacancies. These have the advantage of being able to maintain superposition longer than other candidates, but emit light across a broad range of frequencies, making information retrieval difficult.

    The MIT-Harvard-Sandia team, led by Tim Schröder, experimented instead with silicon-based defects, which emit light in a much narrower range. That advantage, however, comes with its own challenge: the silicon dopant-vacancies need to be chilled to within a few thousands of a degree above absolute zero if they are to maintain a superposition for any length of time.

    That remains a challenge still to be met, however. The import of the current study, published in the journal Nature Communications, lies in the increase in the accuracy of positioning the defects in the diamond.

    To achieve this, scientists at MIT and Harvard first created a sliver of diamond only 200 nanometres thick. Onto this they etched tiny cavities.

    The substrate was then sent to the Sandia laboratories, where each cavity was bombarded with 20 to 30 silicon ions. The process led to only about two percent of the cavities attracting silicon residents.

    Back at MIT a second new process was employed. The diamond sliver was heated to 1000 ºC, at which temperature its component lattice became malleable, allowing the researchers to align more cavities with more silicon particles – taking the total number of dopant-vacancies to 20%.

    Most of the irregularities thus produced were within 50 nanometres of their optimal position, and shone at around 85% of optimal brightness.

    A quantum computer in every household is still a long way off, but this study marks a potentially important step in the journey.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 4:23 pm on January 2, 2017 Permalink | Reply
    Tags: , Electron-photon small-talk could have big impact on quantum computing, , , Qubits   

    From Princeton: “Electron-photon small-talk could have big impact on quantum computing” 

    Princeton University
    Princeton University

    December 22, 2016
    Catherine Zandonella

    In a step that brings silicon-based quantum computers closer to reality, researchers at Princeton University have built a device in which a single electron can pass its quantum information to a particle of light. The particle of light, or photon, can then act as a messenger to carry the information to other electrons, creating connections that form the circuits of a quantum computer.

    The research, published today in the journal Science and conducted at Princeton and HRL Laboratories in Malibu, California, represents a more than five-year effort to build a robust capability for an electron to talk to a photon, said Jason Petta, a Princeton professor of physics.

    1
    Princeton Professor of Physics Jason Petta, from left, and physics graduate students David Zajac and Xiao Mi, have built a device that is a step forward for silicon-based quantum computers, which when built will be able to solve problems beyond the capabilities of everyday computers. The device isolates an electron so that can pass its quantum information to a photon, which can then act as a messenger to carry the information to other electrons to form the circuits of the computer. (Photo by Denise Applewhite, Office of Communications)

    “Just like in human interactions, to have good communication a number of things need to work out — it helps to speak the same language and so forth,” Petta said. “We are able to bring the energy of the electronic state into resonance with the light particle, so that the two can talk to each other.”

    The discovery will help the researchers use light to link individual electrons, which act as the bits, or smallest units of data, in a quantum computer. Quantum computers are advanced devices that, when realized, will be able to perform advanced calculations using tiny particles such as electrons, which follow quantum rules rather than the physical laws of the everyday world.

    Each bit in an everyday computer can have a value of a 0 or a 1. Quantum bits — known as qubits — can be in a state of 0, 1, or both a 0 and a 1 simultaneously. This superposition, as it is known, enables quantum computers to tackle complex questions that today’s computers cannot solve.

    Simple quantum computers have already been made using trapped ions and superconductors, but technical challenges have slowed the development of silicon-based quantum devices. Silicon is a highly attractive material because it is inexpensive and is already widely used in today’s smartphones and computers.

    2
    The qubit consists of a single electron that is trapped below the surface of a silicon chip (gray). The green, pink and purple wires on top of the silicon structure deliver precise voltages to the qubit. The purple plate reduces electronic interference that can destroy the qubit’s quantum information. By adjusting the voltages in the wires, the researchers can trap a single electron in a double quantum dot and adjust its energy so that it can communicate its quantum information to a nearby photon. (Photo courtesy of the Jason Petta research group, Department of Physics)

    The researchers trapped both an electron and a photon in the device, then adjusted the energy of the electron in such a way that the quantum information could transfer to the photon. This coupling enables the photon to carry the information from one qubit to another located up to a centimeter away.

    Quantum information is extremely fragile — it can be lost entirely due to the slightest disturbance from the environment. Photons are more robust against disruption and can potentially carry quantum information not just from qubit to qubit in a quantum computer circuit but also between quantum chips via cables.

    For these two very different types of particles to talk to each other, however, researchers had to build a device that provided the right environment. First, Peter Deelman at HRL Laboratories, a corporate research-and-development laboratory owned by the Boeing Company and General Motors, fabricated the semiconductor chip from layers of silicon and silicon-germanium. This structure trapped a single layer of electrons below the surface of the chip. Next, researchers at Princeton laid tiny wires, each just a fraction of the width of a human hair, across the top of the device. These nanometer-sized wires allowed the researchers to deliver voltages that created an energy landscape capable of trapping a single electron, confining it in a region of the silicon called a double quantum dot.

    The researchers used those same wires to adjust the energy level of the trapped electron to match that of the photon, which is trapped in a superconducting cavity that is fabricated on top of the silicon wafer.

    Prior to this discovery, semiconductor qubits could only be coupled to neighboring qubits. By using light to couple qubits, it may be feasible to pass information between qubits at opposite ends of a chip.

    The electron’s quantum information consists of nothing more than the location of the electron in one of two energy pockets in the double quantum dot. The electron can occupy one or the other pocket, or both simultaneously. By controlling the voltages applied to the device, the researchers can control which pocket the electron occupies.

    “We now have the ability to actually transmit the quantum state to a photon confined in the cavity,” said Xiao Mi, a graduate student in Princeton’s Department of Physics and first author on the paper. “This has never been done before in a semiconductor device because the quantum state was lost before it could transfer its information.”

    4
    A fully packaged device for trapping and manipulating single electrons and photons. A series of on-chip electrodes (lower left and upper right) lead to the formation of a double quantum dot that confines a single electron below the surface of the chip. The photon, which is free to move within the full 7-millimeter span of the cavity, exchanges quantum information with the electron inside the double quantum dot. (Photo courtesy of the Jason Petta research group, Department of Physics)

    The success of the device is due to a new circuit design that brings the wires closer to the qubit and reduces interference from other sources of electromagnetic radiation. To reduce this noise, the researchers put in filters that remove extraneous signals from the wires that lead to the device. The metal wires also shield the qubit. As a result, the qubits are 100 to 1,000 times less noisy than the ones used in previous experiments.

    Jeffrey Cady, a 2015 graduate, helped develop the filters to reduce the noise as part of his undergraduate senior thesis, and graduate student David Zajac led the effort to use overlapping electrodes to confine single electrons in silicon quantum dots.

    Eventually the researchers plan to extend the device to work with an intrinsic property of the electron known as its spin. “In the long run we want systems where spin and charge are coupled together to make a spin qubit that can be electrically controlled,” Petta said. “We’ve shown we can coherently couple an electron to light, and that is an important step toward coupling spin to light.”

    David DiVincenzo, a physicist at the Institute for Quantum Information in RWTH Aachen University in Germany, who was not involved in the research, is the author of an influential 1996 paper outlining five minimal requirements necessary for creating a quantum computer. Of the Princeton-HRL work, in which he was not involved, DiVincenzo said: “It has been a long struggle to find the right combination of conditions that would achieve the strong coupling condition for a single-electron qubit. I am happy to see that a region of parameter space has been found where the system can go for the first time into strong-coupling territory.”

    Funding for this research was provided by Army Research Office grant No. W911NF-15-1-0149, the Gordon and Betty Moore Foundation’s EPiQS Initiative through grant GBMF4535, and the National Science Foundation (DMR-1409556 and DMR-1420541). The material is based upon work supported by the U.S. Department of Defense under contract H98230-15-C0453.

    The paper, Strong Coupling of a Single Electron in Silicon to a Microwave Photon by X. Mi, J. V. Cady, D. M. Zajac, P. W. Deelman, J. R. Petta, was published in the journal Science online on Thursday, Dec. 22.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: