From The DOE’s Brookhaven National Laboratory And Stoney Brook University-SUNY: “Quantum Chemistry Finds a New Path on Quantum Devices”

From The DOE’s Brookhaven National Laboratory

And

Stoney Brook bloc

Stoney Brook University-SUNY

9.13.22

Denise Yazak
dyazak@bnl.gov

A new quantum algorithm solves a critical problem in quantum chemistry through gradual adaptation along a specially chosen geometric path.

1
In calculating the potential energy surface of the chemical reaction of H2 ;+ D2 → 2HD, the new algorithm (green diamonds) outperforms the previous algorithm (orange squares) in finding the most accurate solution (blue line).

A team of researchers from the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and Stony Brook University-SUNY have devised a new quantum algorithm to compute the lowest energies of molecules at specific configurations during chemical reactions, including when their chemical bonds are broken. As described in Physics Review Research [below], compared to similar existing algorithms, including the team’s previous method, the new algorithm will significantly improve scientists’ ability to accurately and reliably calculate the potential energy surface in reacting molecules.

For this work, Deyu Lu, a Center for Functional Nanomaterials (CFN) [below] physicist at Brookhaven Lab, worked with Tzu-Chieh Wei, an associate professor specializing in quantum information science at the C.N. Yang Institute for Theoretical Physics at Stony Brook University-SUNY, Qin Wu, a theorist at CFN, and Hongye Yu, a Ph.D. student at Stony Brook.

“Understanding the quantum mechanics of a molecule, how it behaves at an atomic level, can provide key insight into its chemical properties, like its stability and reactivity,” said Lu.

One particular property that has been a challenge to determine is a molecule’s ground state: the point where the molecule’s total electronic energy (including kinetic and potential energy) is at its lowest and nothing outside of that “molecular system” is exciting or charging the molecule’s electrons. When the atomic structure of a chemical system gets more complex, as in a large molecule, many more electrons can interact. Those interactions make calculating the ground state of complex molecules extremely difficult.

The new quantum algorithm improves on the previous algorithm to tackle this problem in a creative way. It exploits a smooth, geometric deformation made by continuously varying bond lengths or bond angles in the molecule’s structure. With this approach the scientists say they can calculate the ground state of molecules very accurately, even as chemical bonds are breaking and reforming during chemical reactions.

Building the Groundwork

“When solely relying on traditional computing methods, this ground state problem contains too many variables to solve—even on the most powerful supercomputers,” said Lu.

You can think of an algorithm as a set of steps to solve a particular problem. Classical computers can run complex algorithms, but as they get larger and more involved, they can become too difficult or time-consuming for classical computers to feasibly solve. Quantum computers can speed up the process by leveraging the rules of quantum mechanics.

In classical computing, data is stored in bits that have a value of 1 or 0. A quantum bit, known as a qubit, can have a value beyond just 0 or 1, it can even have a value of 0 and 1, in a so-called quantum superposition. In principle, these more “flexible” qubits can store a larger amount of information than classical bits. If scientists can find ways to harness the information-carrying capacity of qubits, computing power can expand exponentially with each additional qubit.

Qubits, however, are quite fragile. They can often break down when information is being extracted. When a quantum device interacts with the surrounding environment, it can generate noise or interference that destroys the quantum state. Temperature changes, vibrations, electromagnetic interference, and even material defects can also cause qubits to lose information.

To compensate for these pitfalls, scientists developed a hybrid solution that takes advantage of both classical computing algorithms, which are more stable and practical.

With seed grant funding from Stony Brook University-SUNY, Lu and Wei began researching on hybrid classical and quantum computing approaches in 2019. This annual grant promotes collaboration between Brookhaven National Laboratory and Stony Brook University-SUNY by funding joint research initiatives that align with the missions of both institutions. With this initial work, Lu and Wei first focused on solving the ground state problem by replacing the most “expensive” classical algorithms—the ones that were much more complex and required significantly more steps (and more computing time) to complete—with quantum ones.

Stretching bonds, creating new paths

The researchers note that existing quantum algorithms all come with drawbacks for solving the ground state problem, including the one Wei and Yu developed in 2019. While some popular algorithms are accurate when a molecule is at its equilibrium geometry—its natural arrangement of atoms in three dimensions—those algorithms can become unreliable when the chemical bonds are broken at large atomic distances. Bond formation and dissociation play a role in many applications, such as predicting how much energy it takes to get a chemical reaction started, so scientists needed a way to tackle this problem as molecules react. They needed new quantum algorithms that can describe bond breaking.

For this new version of the algorithm, the team worked with the Brookhaven-Lab-led Co-design Center for Quantum Advantage (C2QA), which was formed in 2020. Wei contributes to the center’s software thrust, which specializes in quantum algorithms. The team’s new algorithm uses an adiabatic approach—one that makes gradual changes—but with some adaptations that ensure it remains reliable when chemical bonds are broken.

“An adiabatic process works by gradually adapting the conditions of a quantum mechanical system,” explained Lu. “In a way, you are reaching a solution in very small steps. You evolve the system from a simple, solvable model to the final target, typically a more difficult model. In addition to the ground state, however, a many-electronic system has many excited states at higher energies. Those excited states can pose a challenge when using this method to calculate the ground state.”

Wei compared an adiabatic algorithm to driving along a highway, “if you are traveling from one town to the next, there are several paths to get there, but you want to find the safest and most efficient one.”

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At a particular O-H distance within an H2O molecule, there are multiple energy crossing points (a). This is the reason that the initial Adiabatic Algorithm fails. In contrast, the new algorithm, where the distance starts at a closer point and gradually moves further has energy levels smoothly connected without any crossing (b).

In the case of quantum chemistry, the key is to find a large enough “energy gap” between the ground state and excited states where no electron states exist. With a large enough gap, the vehicles in the highway metaphor won’t “cross lanes,” so their paths can be accurately traced.

“A large gap means that you can go faster, so, in a sense, you’re trying to find a less crowed highway to drive faster without hitting anything,” said Wei.

“With these algorithms, the entrance of the path is a well-defined, simple solution from classical computing,” Wei noted. “We also know where the exit is—the ground state of the molecule—and we were trying to find a way to connect it to the entrance in the most natural way, a straight line.

“We did that in our first paper, but the straight line had roadblocks caused by the energy gap closing and paths crossing. Now we have a better solution.”

When the scientists tested the algorithm, they demonstrated that even with finite bond length changes, the improved version still performed accurately for the ground state.

“We went beyond our comfort zone, because chemistry is not our focus,” said Wei. “But it was good to find an application like this and foster this kind of collaboration with CFN. It’s important to have different perspectives in research.”

He noted the accumulated effort of many people. “In the grand scheme, I think we’re making a small contribution, but this could be a foundation for other work in these fields,” he said. “This research is not only foundational, but a great illustration of how different institutions and facilities can come together to leverage their areas of expertise.”

The research on the quantum algorithmic development in this work was supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Co-design Center for Quantum Advantage (C2QA), while quantum chemistry applications used the theory and computation resources of the Center for Functional Nanomaterials (CFN), a U.S. Department of Energy Office of Science User Facility at Brookhaven National Laboratory. Additional funding was provided by the National Science Foundation.

Science paper:
Physics Review Research

See the full article here .


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Stoney Brook campus

Stony Brook University-SUNY’s reach extends from its 1,039-acre campus on Long Island’s North Shore–encompassing the main academic areas, an 8,300-seat stadium and sports complex and Stony Brook Medicine–to Stony Brook Manhattan, a Research and Development Park, four business incubators including one at Calverton, New York, and the Stony Brook Southampton campus on Long Island’s East End. Stony Brook also co-manages Brookhaven National Laboratory, joining Princeton University, The University of Chicago, Stanford University, and The University of California on the list of major institutions involved in a research collaboration with a national lab.
And Stony Brook is still growing. To the students, the scholars, the health professionals, the entrepreneurs and all the valued members who make up the vibrant Stony Brook community, this is a not only a great local and national university, but one that is making an impact on a global scale.

Brookhaven Campus

One of ten national laboratories overseen and primarily funded by the The DOE Office of Science, The DOE’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.

BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.

Major programs

Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:

Nuclear and high-energy physics
Physics and chemistry of materials
Environmental and climate research
Nanomaterials
Energy research
Nonproliferation
Structural biology
Accelerator physics

Operation

Brookhaven National Lab was originally owned by the Atomic Energy Commission and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University and Battelle Memorial Institute. From 1947 to 1998, it was operated by Associated Universities, Inc. (AUI), but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.

Foundations

Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology to have a facility near Boston, Massachusetts. Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia University, Cornell University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, University of Pennsylvania, University of Rochester, and Yale University.

Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.

On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).

Research and facilities

Reactor history

In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.

Accelerator history

In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.

BNL Cosmotron 1952-1966.

The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).

BNL Alternating Gradient Synchrotron (AGS).

The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.

In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.

The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.

The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II. [below].

BNL National Synchrotron Light Source.

After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider (CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.

On January 9, 2020, it was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility [Jlab] as the future Electron–ion collider (EIC) in the United States.

In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.

Other discoveries

In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.

Major facilities

Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.

Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.

BNL National Synchrotron Light Source II, Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years. NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.

Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
Accelerator Test Facility, generates, accelerates and monitors particle beams.
Tandem Van de Graaff, once the world’s largest electrostatic accelerator.

Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University-SUNY.

Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.

Off-site contributions

It is a contributing partner to the ATLAS experiment, one of the four detectors located at the The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Large Hadron Collider(LHC).

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map.

Iconic view of the European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear] [Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] ATLAS detector.

It is currently operating at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] near Geneva, Switzerland.

Brookhaven was also responsible for the design of the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.

DOE’s Oak Ridge National Laboratory Spallation Neutron Source annotated.

Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China.

Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China .


BNL Center for Functional Nanomaterials.

BNL National Synchrotron Light Source II.

BNL NSLS II.

BNL Relative Heavy Ion Collider Campus.

BNL/RHIC Phenix detector.