Nav: Home

The best of both worlds: how to solve real problems on modern quantum computers

July 11, 2019

In recent years, quantum devices have become available that enable researchers -- for the first time -- to use real quantum hardware to begin to solve scientific problems. However, in the near term, the number and quality of qubits (the basic unit of quantum information) for quantum computers are expected to remain limited, making it difficult to use these machines for practical applications.

A hybrid quantum and classical approach may be the answer to tackling this problem with existing quantum hardware. Researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory and Los Alamos National Laboratory, along with researchers at Clemson University and Fujitsu Laboratories of America, have developed hybrid algorithms to run on quantum machines and have demonstrated them for practical applications using IBM quantum computers (see below for description of Argonne's role in the IBM Q Hub at Oak Ridge National Laboratory [ORNL]) and a D-Wave quantum computer.

"This approach will enable researchers to use near-term quantum computers to solve applications that support the DOE mission. For example, it can be applied to find community structures in metabolic networks or a microbiome." -- Yuri Alexeev, principal project specialist, Computational Science division

The team's work is presented in an article entitled "A Hybrid Approach for Solving Optimization Problems on Small Quantum Computers" that appears in the June 2019 issue of the Institute of Electrical and Electronics Engineers (IEEE) Computer Magazine. 

Concerns about qubit connectivity, high noise levels, the effort required to correct errors, and the scalability of quantum hardware have limited researchers' ability to deliver the solutions that future quantum computing promises.

The hybrid algorithms that the team developed employ the best features and capabilities of both classical and quantum computers to address these limitations. For example, classical computers have large memories capable of storing huge datasets -- a challenge for quantum devices that have only a small number of qubits. On the other hand, quantum algorithms perform better for certain problems than classical algorithms.

To distinguish between the types of computation performed on two completely different types of hardware, the team referred to the classical and quantum stages of hybrid algorithms as central processing units (CPUs) for classical computers and quantum processing units (QPUs) for quantum computers.

The team seized on graph partitioning and clustering as examples of practical and important optimization problems that can already be solved using quantum computers: a small graph problem can be solved directly on a QPU, while larger graph problems require hybrid quantum-classical approaches.

As a problem became too large to run directly on quantum computers, the researchers used decomposition methods to break the problem down into smaller pieces that the QPU could manage -- an idea they borrowed from high-performance computing and classical numerical methods.

All the pieces were then assembled into a final solution on the CPU, which not only found better parameters, but also identified the best sub-problem size to solve on a quantum computer.

Such hybrid approaches are not a silver bullet; they do not allow for quantum speedup because using decomposition schemes limits speed as the size of the problem increases. In the next 10 years, though, expected improvements in qubits (quality, count, and connectivity), error correction, and quantum algorithms will decrease runtime and enable more advanced computation.

"In the meantime," according to Yuri Alexeev, principal project specialist in the Computational Science division, "this approach will enable researchers to use near-term quantum computers to solve applications that support the DOE mission. For example, it can be applied to find community structures in metabolic networks or a microbiome."
Additional paper authors include Ruslan Shaydulin and Ilya Safro of Clemson University, Hayato Ushijima-Mwesigwa of Fujitsu Laboratories of America, and Christian F.A. Negre and Susan M. Mniszewski of Los Alamos National Laboratory.

This research leveraged the computing resources of the Argonne  Leadership Computing Facility, a DOE Office of Science User Facility; IBM quantum computers at the Oak Ridge National Laboratory IBM Q hub; and a D-Wave 2000Q quantum computer provided by the DOE National Nuclear Security Administration's Advanced Simulation and Computing Program at Los Alamos National Laboratory.

About the IBM Q Hub at Oak Ridge National Laboratory...
The IBM Q Network is the world's first community of Fortune 500 companies, startups, academic institutions and research labs working with IBM to advance quantum computing and explore practical applications for business and science. As one of the member organizations of the IBM Q Hub at ORNL, Argonne is developing quantum algorithms to help tackle challenges in chemistry and physics. The new algorithms will also be used to model and simulate quantum network architectures and develop hybrid quantum-classical architectures, which combine the power of quantum processors with Argonne's world-class supercomputing resources. Membership in the IBM Q Hub is enabling Argonne researchers to leverage their expertise in scalable algorithms across a broad set of multidisciplinary scientific applications and explore the impact of quantum computing on key areas including quantum chemistry and quantum materials.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.

The U.S. Department of Energy's Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit

DOE/Argonne National Laboratory

Related Quantum Computers Articles:

Hot qubits break one of the biggest constraints to practical quantum computers
A proof-of-concept published today in Nature promises warmer, cheaper and more robust quantum computing.
Future quantum computers may pose threat to today's most-secure communications
Quantum computers that are exponentially faster than any of our current classical computers and are capable of code-breaking applications could be available in 12 to 15 years, posing major risks to the security of current communications systems, according to a new RAND Corporation report.
Novel error-correction scheme developed for quantum computers
Experimental quantum computers are plagued with errors. Here Dr Arne Grimsmo from the University of Sydney and colleagues from RMIT and the University of Queensland offer a novel method to reduce errors in a scheme applicable across different types of quantum hardware.
FEFU scientists developed method to build up functional elements of quantum computers
Scientists from Far Eastern Federal University (FEFU, Vladivostok, Russia), together with colleagues from FEB RAS, China, Hong Kong, and Australia, manufactured ultra-compact bright sources based on IR-emitting mercury telluride (HgTe) quantum dots (QDs), the future functional elements of quantum computers and advanced sensors.
ORNL researchers advance performance benchmark for quantum computers
Researchers at the Department of Energy's Oak Ridge National Laboratory (ORNL) have developed a quantum chemistry simulation benchmark to evaluate the performance of quantum devices and guide the development of applications for future quantum computers.
Quantum computers learn to mark their own work
A new test to check if a quantum computer is giving correct answers to questions beyond the scope of traditional computing could help the first quantum computer that can outperform a classical computer to be realised.
Blanket of light may give better quantum computers
Researchers from DTU Physics describe in an article in Science, how--by simple means -- they have created a 'carpet' of thousands of quantum-mechanically entangled light pulses.
One step closer future to quantum computers
Physicists at Uppsala University in Sweden have identified how to distinguish between true and 'fake' Majorana states in one of the most commonly used experimental setups, by means of supercurrent measurements.
Dartmouth research advances noise cancelling for quantum computers
The characterization of complex noise in quantum computers is a critical step toward making the systems more precise.
Spreading light over quantum computers
Scientists at Linköping University have shown how a quantum computer really works and have managed to simulate quantum computer properties in a classical computer.
More Quantum Computers News and Quantum Computers Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Making Amends
What makes a true apology? What does it mean to make amends for past mistakes? This hour, TED speakers explore how repairing the wrongs of the past is the first step toward healing for the future. Guests include historian and preservationist Brent Leggs, law professor Martha Minow, librarian Dawn Wacek, and playwright V (formerly Eve Ensler).
Now Playing: Science for the People

#566 Is Your Gut Leaking?
This week we're busting the human gut wide open with Dr. Alessio Fasano from the Center for Celiac Research and Treatment at Massachusetts General Hospital. Join host Anika Hazra for our discussion separating fact from fiction on the controversial topic of leaky gut syndrome. We cover everything from what causes a leaky gut to interpreting the results of a gut microbiome test! Related links: Center for Celiac Research and Treatment website and their YouTube channel
Now Playing: Radiolab

The Flag and the Fury
How do you actually make change in the world? For 126 years, Mississippi has had the Confederate battle flag on their state flag, and they were the last state in the nation where that emblem remained "officially" flying.  A few days ago, that flag came down. A few days before that, it coming down would have seemed impossible. We dive into the story behind this de-flagging: a journey involving a clash of histories, designs, families, and even cheerleading. This show is a collaboration with OSM Audio. Kiese Laymon's memoir Heavy is here. And the Hospitality Flag webpage is here.