Quantum Research Highlights

The Quantum Systems Accelerator (QSA) Center will Pioneer Quantum Technologies for Discovery Science

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Sandia National Laboratories will serve as the leading partner in one of five national research centers for quantum information science established by the Department of Energy today. The QSA Center will catalyze U.S. leadership in quantum information science, and strengthen the nation’s research community to accelerate commercialization

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Sandia builds a testbed for powerful quantum computing hardware and scientific applications

Try this thought experiment: imagine a small measurable quantity of something-perhaps a grain of sand or a point of light-then cut it in half, again and again. When you reach the smallest quantity, such as a photon of light, you will have created an indivisible quantum particle. Scientists and engineers can control these subatomic particles, or qubits, to design, build, and test revolutionary computers to answer extremely complex scientific questions. Sandia National Laboratories’ Quantum Scientific Computing Open User Testbed (QSCOUT) project takes on both challenges.

The five-year, $25.1 million QSCOUT project funded by the U.S. Department of Energy (DOE) Office of Science Advanced Scientific Computing Research (ASCR) program is advancing research on trapped ion quantum computer technology, one of the major competing technologies for producing full-scale quantum computers. Scientists in an ideal quantum computing world could access processing power exponentially greater than what is available now, even with supercomputers, to solve special classes of exascale problems. Already they are studying multidimensional problems involving simultaneous computation, communication, and sensing (global cybersecurity, for example) using complex mathematical processes known as algorithms.

Processing such volumes of data in a matter of seconds requires a new type of information science. #160; QSCOUT aims to meet this need by providing unrestricted access to quantum hardware internals– the quantum gates and underlying pulse sequences– enabling users to adapt and modify them. Sandia will eventually support and advise users in the functionality of the QSCOUT testbeds, allowing them to realize the potential of high-fidelity quantum computing in a way not yet available to most researchers.

A major challenge confronts quantum technology: the qubits it relies on can be unstable and easily disturbed by the slightest changes in their environment. When that happens, they may experience decoherence, the process whereby they decay and eventually disappear. According to Sandia researcher and QSCOUT project lead, Peter Maunz, trapped ion technology has enormous potential to avoid the decoherence (also called noise) and gate error problems that make it difficult to build and to operate a working quantum computer with integrated quantum circuits.

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Maunz explains: "Because trapped ions are identical and suspended by electric fields in a vacuum, they feature identical, nearly perfect qubits well isolated from the noise of the environment and able, therefore, to store and process information faithfully." Further, he says, "While current small-scale quantum computers without quantum error correction are still noisy devices, quantum gates with the lowest noise have been realized with trapped-ion technology."

With its focus on trapped ion quantum computer technology, QSCOUT builds on Sandia’s physics and engineering expertise in fabricating microelectromechanical systems and complementary metal oxide semiconductor devices at the Labs’ Microsystems and Engineering Sciences Applications (MESA) facility.

QSCOUT will also assess the potential of near-term quantum hardware by giving researchers access to a trapped-ion quantum computer to address scientific computing applications of interest to other DOE and DOE ASCR projects and programs. With orders of magnitude more power as they gain qubits, quantum computers will help researchers create and optimize complex algorithms that take advantage of quantum computing.

Sandia physics, computer engineering expertise helping to correct quantum computing errors

Quantum computers face challenges unknown to conventional computers. Sandia National Laboratories plays two important roles supporting the Logical Qubits (LogiQ) program, a broader effort by the Intelligence Advanced Research Projects Activity (IARPA) to address two of those challenges-decoherence and gate error.

Quantum computers are affected by their environment to a far greater degree than conventional computers. Today’s laptops may shut down in extreme heat, but quantum computers can be affected by vibrations, temperature fluctuations, electromagnetic waves and other interactions with the outside environment, any of which can cause quantum decoherence. A loss of quantum coherence can prevent an algorithm from running successfully. The second challenge is the difficulty of implementing quantum logic gates with perfect accuracy. Quantum gates operate on a small number of quantum bits or ‘qubits’, which are somewhat analogous to the familiar 0-1 binary bit in a conventional computer, to implement the steps in a program, known as a quantum circuit. But when gates fail (about 1% of the time), those errors cannot be corrected using traditional methods, because measuring qubits causes them to decohere. Running long programs correctly will require new quantum error correction algorithms. To achieve this, many hardware-level physical qubits must be combined to create virtual qubits that are protected against decoherence and gate errors and are known as "logical qubits".

IARPA’s LogiQ program seeks to overcome the limitations of current multi-qubit systems by demonstrating the first, low-error logical qubit system. Each of four LogiQ performer teams is pursuing their own unique solution to demonstrate a single logical qubit with dynamic and repetitive error correction capabilities. These approaches involve building systems of about 15 carefully interconnected, physical qubits that will execute a carefully choreographed error-correction algorithm that will protect their encoded logical qubit from errors. Two of the performer teams are building devices based on superconducting transmon qubits, while the other two teams are using trapped-ion qubits.

Separate teams of scientists within Sandia are supporting IARPA’s goals in the LogiQ program by serving as a partner to IARPA in two important roles. A team of trapped-ion qubit experts, led by Melissa Revelle after the departure of the projects founder and original PI Peter Maunz, is designing, fabricating, and testing new surface-electrode ion traps that are made available for use by the performer teams as a Government Furnished Capability. A second, separate team from Sandia’s Quantum Performance Lab serves in a Test and Evaluation (T&E) capacity. Here they are exploring evaluation protocols that can help IARPA understand the nuances of the performance of the different physical instantiations of a single logical qubit to use in carrying out T&E of the performers’ work. Along the way, the performers must improve their physical qubit gates to satisfy the requirements of their chosen error correction scheme, and Sandia has defined protocols for characterizing and testing these incremental systems as well.

Sandia’s dual roles draw on the deep and varied expertise in quantum information science that jointly resides in several departments dispersed across the Labs. This expertise as been built up through many projects, starting in the early 2000’s and, most notably, creating a cross-Labs, highly interdisciplinary team as an upshot of the Quantum Information Science & Technology Grand Challenge Laboratory Directed R&D (LDRD) (2008-2010). Solving the problems of decoherence and gate errors requires integrating the perspectives of these Sandia physicists and engineers. "We’ve discovered a tremendous amount about the detailed behavior of a logical qubit system in our Test & Evaluation support to IARPA and the four performer teams," said Robin Blume-Kohout, lead scientist of the Quantum Performance Lab, "and we’re using the new science that we’ve learned to support the National Quantum Initiative and the U.S. national effort to excel in quantum computing."