From University of Rochester (US): “Researchers confront major hurdle in quantum computing”

From University of Rochester (US)

May 4, 2021
Lindsey Valich
lvalich@ur.rochester.edu

1
A quantum processor semiconductor chip is shown connected to a circuit board. Credit: J. Adam Fenster/University of Rochester.

In a series of papers Rochester researchers report major strides in improving the transfer of information in quantum systems.

Quantum science has the potential to revolutionize modern technology with more efficient computers, communication, and sensing devices. But challenges remain in achieving these technological goals, especially when it comes to effectively transferring information in quantum systems.

A regular computer consists of billions of transistors, called bits. Quantum computers, on the other hand, are based on quantum bits, also known as qubits, which can be made from a single electron.

Unlike ordinary transistors, which can be either “0” (off) or “1” (on), qubits can be both “0” and “1” at the same time. The ability of individual qubits to occupy these so-called superposition states, where they are in multiple states simultaneously, underlies the great potential of quantum computers. Just like ordinary computers, however, quantum computers need a way to transfer quantum information between distant qubits—and that presents a major experimental challenge.

In a series of papers published in Nature Communications, researchers at the University of Rochester, including John Nichol, an assistant professor of physics and astronomy, and graduate students Yadav Kandel and Haifeng Qiao, the lead authors of the papers, report major strides in enhancing quantum computing by improving the transfer of information between electrons in quantum systems.

Utilizing a new route

In one paper Nature Communications, the researchers demonstrated a route of transferring information between qubits, called adiabatic quantum state transfer (AQT), for the first time with electron-spin qubits. Unlike most methods of transferring information between qubits, which rely on carefully tuned electric or magnetic-field pulses, AQT isn’t as affected by pulse errors and noise.

To envision how AQT works, imagine you are driving your car and want to park it. If you don’t hit your brakes at the proper time, the car won’t be where you want it, with potential negative consequences. In this sense, the control pulses—the gas and brake pedals—to the car must be tuned carefully. AQT is different in that it doesn’t really matter how long you press the pedals or how hard you press them: the car will always end up in the right spot. As a result, AQT has the potential to improve the transfer of information between qubits, which is essential for quantum networking and error correction.

The researchers demonstrated AQT’s effectiveness by exploiting entanglement—one of the basic concepts of quantum physics in which the properties of one particle affect the properties of another, even when the particles are separated by a large distance. The researchers were able to use AQT to transfer one electron’s quantum spin state across a chain of four electrons in semiconductor quantum dots—tiny, nanoscale semiconductors with remarkable properties. This is the longest chain over which a spin state has ever been transferred, tying the record set by the researchers in a previous Nature paper.

“Because AQT is robust against pulse errors and noise, and because of its major potential applications in quantum computing, this demonstration is a key milestone for quantum computing with spin qubits,” Nichol says.

Exploiting a strange state of matter

In a second paper Nature Communications, the researchers demonstrated another technique of transferring information between qubits, using an exotic state of matter called time crystals. A time crystal is a strange state of matter in which interactions between the particles that make up the crystal can stabilize oscillations of the system in time indefinitely. Imagine a clock that keeps ticking forever; the pendulum of the clock oscillates in time, much like the oscillating time crystal.

By implementing a series of electric-field pulses on electrons, the researchers were able to create a state similar to a time crystal. They found that they could then exploit this state to improve the transfer of an electron’s spin state in a chain of semiconductor quantum dots.

“Our work takes the first steps toward showing how strange and exotic states of matter, like time crystals, can potentially by used for quantum information processing applications, such as transferring information between qubits,” Nichol says. “We also theoretically show how this scenario can implement other single- and multi-qubit operations that could be used to improve the performance of quantum computers.”

Both AQT and time crystals, while different, could be used simultaneously with quantum computing systems to improve performance.

“These two results illustrate the strange and interesting ways that quantum physics allows for information to be sent from one place to another, which is one of the main challenges in constructing viable quantum computers and networks,” Nichol says.

See the full article here .

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U Rochester

The University of Rochester (US) is a private research university in Rochester, New York. The university grants undergraduate and graduate degrees, including doctoral and professional degrees.

The University of Rochester (US) enrolls approximately 6,800 undergraduates and 5,000 graduate students. Its 158 buildings house over 200 academic majors. According to the National Science Foundation (US), Rochester spent $370 million on research and development in 2018, ranking it 68th in the nation. The university is the 7th largest employer in the Finger lakes region of New York.

The College of Arts, Sciences, and Engineering is home to departments and divisions of note. The Institute of Optics was founded in 1929 through a grant from Eastman Kodak and Bausch and Lomb as the first educational program in the US devoted exclusively to optics and awards approximately half of all optics degrees nationwide and is widely regarded as the premier optics program in the nation and among the best in the world. The Departments of Political Science and Economics have made a significant and consistent impact on positivist social science since the 1960s and historically rank in the top 5 in their fields. The Department of Chemistry is noted for its contributions to synthetic organic chemistry, including the first lab based synthesis of morphine. The Rossell Hope Robbins Library serves as the university’s resource for Old and Middle English texts and expertise. The university is also home to Rochester’s Laboratory for Laser Energetics, a Department of Energy (US) supported national laboratory.

The University of Rochester’s Eastman School of Music (US) ranks first among undergraduate music schools in the U.S. The Sibley Music Library at Eastman is the largest academic music library in North America and holds the third largest collection in the United States.

In its history university alumni and faculty have earned 13 Nobel Prizes; 13 Pulitzer Prizes; 45 Grammy Awards; 20 Guggenheim Awards; 5 National Academy of Sciences; 4 National Academy of Engineering; 3 Rhodes Scholarships; 3 National Academy of Inventors; and 1 National Academy of Inventors Hall of Fame.

History

Early history

The University of Rochester traces its origins to The First Baptist Church of Hamilton (New York) which was founded in 1796. The church established the Baptist Education Society of the State of New York later renamed the Hamilton Literary and Theological Institution in 1817. This institution gave birth to both Colgate University(US) and the University of Rochester. Its function was to train clergy in the Baptist tradition. When it aspired to grant higher degrees it created a collegiate division separate from the theological division.

The collegiate division was granted a charter by the State of New York in 1846 after which its name was changed to Madison University. John Wilder and the Baptist Education Society urged that the new university be moved to Rochester, New York. However, legal action prevented the move. In response, dissenting faculty, students, and trustees defected and departed for Rochester, where they sought a new charter for a new university.

Madison University was eventually renamed as Colgate University (US).

Founding

Asahel C. Kendrick- professor of Greek- was among the faculty that departed Madison University for Rochester. Kendrick served as acting president while a national search was conducted. He reprised this role until 1853 when Martin Brewer Anderson of the Newton Theological Seminary in Massachusetts was selected to fill the inaugural posting.

The University of Rochester’s new charter was awarded by the Regents of the State of New York on January 31, 1850. The charter stipulated that the university have $100,000 in endowment within five years upon which the charter would be reaffirmed. An initial gift of $10,000 was pledged by John Wilder which helped catalyze significant gifts from individuals and institutions.

Classes began that November with approximately 60 students enrolled including 28 transfers from Madison. From 1850 to 1862 the university was housed in the old United States Hotel in downtown Rochester on Buffalo Street near Elizabeth Street- today West Main Street near the I-490 overpass. On a February 1851 visit Ralph Waldo Emerson said of the university:

“They had bought a hotel, once a railroad terminus depot, for $8,500, turned the dining room into a chapel by putting up a pulpit on one side, made the barroom into a Pythologian Society’s Hall, & the chambers into Recitation rooms, Libraries, & professors’ apartments, all for $700 a year. They had brought an omnibus load of professors down from Madison bag and baggage… called in a painter and sent him up the ladder to paint the title “University of Rochester” on the wall, and they had runners on the road to catch students. And they are confident of graduating a class of ten by the time green peas are ripe.

For the next 10 years the college expanded its scope and secured its future through an expanding endowment; student body; and faculty. In parallel a gift of 8 acres of farmland from local businessman and Congressman Azariah Boody secured the first campus of the university upon which Anderson Hall was constructed and dedicated in 1862. Over the next sixty years this Prince Street Campus grew by a further 17 acres and was developed to include fraternities houses; dormitories; and academic buildings including Anderson Hall; Sibley Library; Eastman and Carnegie Laboratories the Memorial Art Gallery and Cutler Union.

Twentieth century

Coeducation

The first female students were admitted in 1900- the result of an effort led by Susan B. Anthony and Helen Barrett Montgomery. During the 1890s a number of women took classes and labs at the university as “visitors” but were not officially enrolled nor were their records included in the college register. President David Jayne Hill allowed the first woman- Helen E. Wilkinson- to enroll as a normal student although she was not allowed to matriculate or to pursue a degree. Thirty-three women enrolled among the first class in 1900 and Ella S. Wilcoxen was the first to receive a degree in 1901. The first female member of the faculty was Elizabeth Denio who retired as Professor Emeritus in 1917. Male students moved to River Campus upon its completion in 1930 while the female students remained on the Prince Street campus until 1955.

Expansion

Major growth occurred under the leadership of Benjamin Rush Rhees over his 1900-1935 tenure. During this period George Eastman became a major donor giving more than $50 million to the university during his life. Under the patronage of Eastman the Eastman School of Music (US) was created in 1921. In 1925 at the behest of the General Education Board and with significant support for John D. Rockefeller George Eastman and Henry A. Strong’s family medical and dental schools were created. The university award its first Ph.D that same year.

During World War II Rochester was one of 131 colleges and universities nationally that took part in the V-12 Navy College Training Program which offered students a path to a Navy commission. In 1942, the university was invited to join the Association of American Universities(US) as an affiliate member and it was made a full member by 1944. Between 1946 and 1947 in infamous uranium experiments researchers at the university injected uranium-234 and uranium-235 into six people to study how much uranium their kidneys could tolerate before becoming damaged.

In 1955 the separate colleges for men and women were merged into The College on the River Campus. In 1958 three new schools were created in engineering; business administration and education. The Graduate School of Management was named after William E. Simon- former Secretary of the Treasury in 1986. He committed significant funds to the school because of his belief in the school’s free market philosophy and grounding in economic analysis.

Financial decline and name change controversy

Following the princely gifts given throughout his life George Eastman left the entirety of his estate to the university after his death by suicide. The total of these gifts surpassed $100 million before inflation and as such Rochester enjoyed a privileged position amongst the most well endowed universities. During the expansion years between 1936 and 1976 the University of Rochester’s financial position ranked third, near Harvard University’s(US) endowment and the University of Texas (US) System’s Permanent University Fund. Due to a decline in the value of large investments and a lack of portfolio diversity the university’s place dropped to the top 25 by the end of the 1980s. At the same time the preeminence of the city of Rochester’s major employers began to decline.

In response the University commissioned a study to determine if the name of the institution should be changed to “Eastman University” or “Eastman Rochester University”. The study concluded a name change could be beneficial because the use of a place name in the title led respondents to incorrectly believe it was a public university, and because the name “Rochester” connoted a “cold and distant outpost.” Reports of the latter conclusion led to controversy and criticism in the Rochester community. Ultimately, the name “University of Rochester” was retained.

Renaissance Plan

In 1995 university president Thomas H. Jackson announced the launch of a “Renaissance Plan” for The College that reduced enrollment from 4,500 to 3,600 creating a more selective admissions process. The plan also revised the undergraduate curriculum significantly creating the current system with only one required course and only a few distribution requirements known as clusters. Part of this plan called for the end of graduate doctoral studies in chemical engineering; comparative literature; linguistics; and mathematics the last of which was met by national outcry. The plan was largely scrapped and mathematics exists as a graduate course of study to this day.

Twenty-first century

Meliora Challenge

Shortly after taking office university president Joel Seligman commenced the private phase of the “Meliora Challenge”- a $1.2 billion capital campaign- in 2005. The campaign reached its goal in 2015- a year before the campaign was slated to conclude. In 2016, the university announced the Meliora Challenge had exceeded its goal and surpassed $1.36 billion. These funds were allocated to support over 100 new endowed faculty positions and nearly 400 new scholarships.

The Mangelsdorf Years

On December 17, 2018 the University of Rochester announced that Sarah C. Mangelsdorf would succeed Richard Feldman as President of the University. Her term started in July 2019 with a formal inauguration following in October during Meliora Weekend. Mangelsdorf is the first woman to serve as President of the University and the first person with a degree in psychology to be appointed to Rochester’s highest office.

In 2019 students from China mobilized by the Chinese Students and Scholars Association (CSSA) defaced murals in the University’s access tunnels which had expressed support for the 2019 Hong Kong Protests, condemned the oppression of the Uighurs, and advocated for Taiwanese independence. The act was widely seen as a continuation of overseas censorship of Chinese issues. In response a large group of students recreated the original murals. There have also been calls for Chinese government run CSSA to be banned from campus.

Research

Rochester is a member of the Association of American Universities (US) and is classified among “R1: Doctoral Universities – Very High Research Activity”. Rochester had a research expenditure of $370 million in 2018. In 2008 Rochester ranked 44th nationally in research spending but this ranking has declined gradually to 68 in 2018. Some of the major research centers include the Laboratory for Laser Energetics, a laser-based nuclear fusion facility, and the extensive research facilities at the University of Rochester Medical Center. Recently the university has also engaged in a series of new initiatives to expand its programs in biomedical engineering and optics including the construction of the new $37 million Robert B. Goergen Hall for Biomedical Engineering and Optics on the River Campus. Other new research initiatives include a cancer stem cell program and a Clinical and Translational Sciences Institute. UR also has the ninth highest technology revenue among U.S. higher education institutions with $46 million being paid for commercial rights to university technology and research in 2009. Notable patents include Zoloft and Gardasil. WeBWorK, a web-based system for checking homework and providing immediate feedback for students was developed by University of Rochester professors Gage and Pizer. The system is now in use at over 800 universities and colleges as well as several secondary and primary schools. Rochester scientists work in diverse areas. For example, physicists developed a technique for etching metal surfaces such as platinum; titanium; and brass with powerful lasers enabling self-cleaning surfaces that repel water droplets and will not rust if tilted at a 4 degree angle; and medical researchers are exploring how brains rid themselves of toxic waste during sleep.