Study Shows Quantum Computer can Outperform Classical Computer

A collaborative research group from Google Inc., NASA Ames Research Center, and the Department of Energy’s Oak Ridge National Laboratory has shown that a quantum computer has the ability to outshine a classical computer at specific tasks, a feat called quantum supremacy.

Quantum computers are based on the laws of quantum mechanics and use units called qubits to considerably increase the threshold with which information can be transmitted and processed. Conventional “bits” have a value of either 0 or 1, but qubits are encoded with values of both 0 and 1, or any combination of the same, thus enabling a huge number of possibilities to store data.

Although quantum systems are still in their early stages, they have the ability to be exponentially more robust compared to existing leading classical computing systems. They also hold the potential to revolutionize studies in high-energy physics, chemistry, materials, and across the scientific spectrum.

The study outcomes have been reported in the journal Nature, and offer a proof of concept for quantum supremacy. They also demonstrate a baseline comparison of energy consumption and time-to-solution.

This achievement of quantum supremacy is a testament to the strength of American innovation, and DOE’s Labs are helping lead the way in this groundbreaking area of research. The mastery of quantum technology is creating a new Information Age that offers new ways to process information to benefit science and society.

Paul Dabbar, Under Secretary for Science, U.S. Department of Energy

Here, the quantum computer, developed by Google and named Sycamore, included 53 qubits. The classical computer was ORNL’s Summit, stationed at the Oak Ridge Leadership Computing Facility (OLCF) and ranked as the most robust computer in the world due to its more than 4600 compute nodes.

Both systems carried out a task called random circuit sampling (RCS), patterned particularly to evaluate the performance of quantum devices like Sycamore. It took 200 seconds to perform the simulations on the quantum computer.

After performing the same simulations on Summit, the researchers inferred that to complete the calculations, the world’s most robust system would have taken more than 10,000 years with existing advanced algorithms, thus offering experimental evidence of quantum supremacy and critical information to enable designing future quantum computers.

Apart from being faster than its classical counterpart, Sycamore was also about 10 million times more energy-efficient.

The team also evaluated the performance of individual components to exactly estimate the performance of the Sycamore device as a whole, showing that quantum information exhibits a consistent behavior upon being scaled up—a property crucial for designing large-scale quantum computers.

This experiment establishes that today’s quantum computers can outperform the best conventional computing for a synthetic benchmark. There have been other efforts to try this, but our team is the first to demonstrate this result on a real system.

Travis Humble, Director, Quantum Computing Institute, ORNL

That real system was critical. Scientists at Google and NASA’s Ames Research Center in Silicon Valley who were making efforts to overcome the challenge using NASA resources soon realized that a more robust computer is required. And none of the computers are more robust than ORNL’s Summit.

It was not an easy task to port a quantum calculation to the classical Summit. Initially, the RCS simulator, called qFlex, included a CPU-only implementation. However, Summit acquires much of its world-class speed from NVIDIA graphics processing units (GPUs), which handle computationally intensive math problems while the CPUs direct tasks efficiently.

A library created by the OLCF’s Dmitry Liakh to carry out tensor algebra operations on multicore GPUs and CPUs enabled the researchers to leverage all of Summit which, together with the IBM system’s 512 GB of memory per node, increased the simulation speed 46-fold per node (using 4550 of Summit’s nodes) than the earlier implementation that ran only on CPUs.

That the simulation proving the validity of a next-generation architecture such as quantum was run on ORNL’s Summit is indicative of the lab’s long history of accelerated computing innovation and the necessity of classical supercomputers in realizing the potential of quantum computing.

Jeff Nichols, Associate Laboratory Director for Computing and Computational Sciences, ORNL

ORNL’s Titan was the first pioneering computing system to tap the power of GPUs, enabling it to debut at number one in 2012 and remaining in the top 10 world’s most robust systems until 2018. Titan’s success allowed the Summit to be developed, and in a broad sense, it is driving the design of Frontier, expected to be one of the nation’s first exascale computers when it is launched in 2021.

For more than 10 years, the laboratory has been planning for post-exascale platforms through dedicated research programs in quantum computing, sensing, networking, and quantum materials.

These efforts are focused on accelerating the insights into how near-term quantum computing resources can be used to handle the currently most daunting scientific challenges and support the recently declared National Quantum Initiative, a federal attempt to ensure American leadership in quantum sciences, specifically computing.

Leadership such as this will necessitate systems such as Summit to assure the steady growth from devices like Sycamore to larger-scale quantum systems that are exponentially more robust compared to anything in operation at present.

“Realizing the potential of quantum computing requires partnerships that leverage the strengths of innovators like Google and ORNL,” stated ORNL Director Thomas Zacharia. “This milestone is an inspiration to the next generation of researchers who will help push the frontiers of what’s possible in computing and scientific discovery.”

The study was supported by DOE’s Office of Science. The OLCF is a DOE Office of Science User Facility.

(Video credit: Oak Ridge National Laboratory, U.S. Department of Energy)