Quantum Systems Accelerator
The pace toward flexible, stable quantum computers with capabilities far beyond those of today’s classical machines has been accelerated by research at the Quantum Systems Accelerator, which has been continuously breaking new ground. Although the fundamentals of quantum systems have been known for decades, precision engineering is still needed to create machines that make use of these concepts. Many of the same characteristics that make quantum computing so powerful at this scale also make it difficult to use.
The National Quantum Information Science Research Center is the Quantum Systems Accelerator (QSA). Its goal is to answer big science topics that are now impossible to address with traditional approaches by pursuing new physics frontiers with a science-first approach. In three main technologies superconducting circuits, trapped ions, and neutral atoms QSA is co-designing state-of-the-art quantum devices. QSA brings together dozens of experts who are leaders in quantum engineering and fabrication skills, under the direction of Lawrence Berkeley National Laboratory (Berkeley Lab) and with Sandia National Laboratories as a main partner. Delivering a proven quantum advantage in scientific applications is its ultimate objective.
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By exchanging experimental methods, cutting-edge scalable technologies, and theoretical tools of quantum information across multiple application sectors, the QSA cultivates a highly collaborative atmosphere. In addition to business and academic partners, this collaborative ecosystem comprises 15 institutions worldwide and is essential for its state-of-the-art experiments and for advancing the absolute frontier of quantum physics.
Significant advances in many facets of quantum technology and basic physics have resulted from recent research at QSA, as described in several important:
Advancements in Trapped-Ion Quantum Computing
The trapped-ion quantum computing to scale, function faster, and use novel measurement methods. Trapped-ion systems, a well-established platform that uses electric fields to transport and trap ions and lasers to change their quantum states, provide lengthy chains of interconnected qubits with long coherence periods.
The “Enchilada Trap”: Under the direction of Jonathan Sterk, a team of QSA researchers at Sandia National Laboratories created, manufactured, and conducted initial testing on a revolutionary ion trap chip known as the “enchilada trap.” Up to 200 ions can be stored in this trap. Reducing radiofrequency (RF) power dissipation by elevating RF electrodes and eliminating insulating dielectric material are important developments that assist avoid power dissipation problems that may restrict the size and complexity of traps. The trap lays the foundation for future traps that require orders of magnitude more qubits by incorporating numerous operational zones connected by junctions.
Paper on Parallel Gate Operations: Under the direction of Yingyue Zhu, a QSA team at the University of Maryland tackled a bottleneck in trapped-ion systems, where physical gate operations are normally carried out in a sequential fashion. They were able to demonstrate quantum gate operations in parallel. Because every gate used the same set of motional modes, interference was a problem in earlier installations.
This was resolved by Zhu’s group by commanding qubits in space in many directions at the same time, enabling simultaneous operations with no overhead and no interference. Scaling quantum computing processes, enabling better information flow, increasing speed and processing power, and improving stability by minimizing decoherence through quicker operations are all made possible by this invention.
Large-Scale Entanglement Research: Or Katz from Chris Monroe’s team headed a Duke University QSA group that investigated entangling multiple ions simultaneously as a way to scale up quantum processors. They created a method known as “squeezing” that allows several qubits to be entangled in one group at once.
Instead of the usual pairwise entanglement, the researchers may entangle the spins of several ions simultaneously by using this technique, which modifies the scale of ions’ motion or position in a spin-dependent manner. This innovative method opens up new possibilities for applications of quantum information by efficiently generating quantum entangling processes whose structure would be difficult to create using conventional paired methods.
Mid-Circuit Measurements Study: Daiwei Zhu and colleagues at the University of Maryland’s QSA research group investigated the special possibilities that mid-circuit measurements offer. The fact that measuring one qubit may inadvertently impact neighboring qubits if it is not appropriately segregated is a serious problem for many quantum computing designs.
To get around this, the team used precise voltage modification to spatially separate certain ion chain segments, enabling isolated ions to be shuttled away for measurement without affecting other segments. In order to give classically verifiable proof of quantum advantage, they used this approach to develop two interactive protocols: one based on a Computational Bell Test and the other on the Learning With Errors (LWE) problem. This was the first example of defining quantumness computationally and provided a model for cryptographic procedures that exhibit quantumness by interacting with a classical verifier. It is also evident that mid-circuit measurements can be used to improve the efficiency of quantum operations and troubleshoot quantum structures.
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Exploring Physics with Quantum Devices and Techniques
The “QSA Harnesses Quantum Devices and Techniques to Explore Physics – QSA” describes how QSA co-designs state-of-the-art quantum devices spanning several technologies and uses quantum devices and techniques to investigate new physics frontiers.
Research on Increased Quantum Coherence: By enhancing the precision of exact measurements, an experimental team under the direction of Principal Investigator Jun Ye and JILA (a joint institute at the University of Colorado Boulder and NIST) proved the viability of general relativity. They used over 100,000 ultracold strontium atoms in an optical lattice to explore time dilation on a millimeter-scale atomic ensemble with previously unheard-of precision. This study set a new benchmark for accuracy and quantum coherence by detecting minute variations in time caused by gravity 50 times more accurately than earlier clocks. By varying the depth of optical traps to optimize coherence times and measurement stability, the team also concentrated on enhancing control over the clock’s quantum states.
Sensing Beyond the Standard Quantum Limit: At JILA, a QSA team under the direction of Professor James K. Thompson developed a method for improving a quantum sensor’s accuracy by surpassing the standard quantum limit (SQL). Atomic randomness restricts precision to the SQL in a typical matter-wave interferometer.
In order to increase the interferometer results by up to 1.7 dB, this research employed quantum entanglement, which is the linking of the quantum states of about 700 ultracold rubidium atoms. In order to enhance light-atom interaction and enable sophisticated quantum effects, they aimed the rubidium atoms within a high-finesse optical cavity. The team employed two methods: one that used light as a shared quantum network for atoms to collaborate and be “quieter” and another that used light to measure and cancel quantum noise. This invention expands the potential for extremely accurate physics measurements.
Non-Invasive Screening Method: Using a nitrogen-vacancy (NV)-based quantum sensor, researchers at Sandia National Laboratories, under the direction of Andrew (Andy) Mounce, Pauli Kehayias, and Luca Bass, created a non-invasive technique to measure microwave frequency magnetic fields.
This method confirms the expected behavior of quantum devices in comparison to simulations and enables early, sensitive screening for faults without causing damage to the devices. This study expands on previous research by the same group that examined localized electrical shorts in ion traps and used this capacity to measure higher frequency magnetic fields that are important for other quantum computing platforms, such as superconducting and trapped-ion systems.
MagnetoARPES Technique: An adaptation of Angle-Resolved Photoemission Spectroscopy (ARPES), the magnetoARPES technique was developed by a group at Lawrence Berkeley National Laboratory (Berkeley Lab). In the past, electron trajectories were altered when a magnetic field was applied during ARPES observations. By limiting the magnetic field to a small layer (around 100 micrometers from the sample surface), the innovative magnetoARPES approach addresses this issue.
High-resolution measurements of electron energy and emission angles were made possible by the utilization of Berkeley Lab’s top-notch synchrotron light source, which produced powerful, concentrated X-ray beams on thin graphene samples that allowed photoelectrons to pass through the confined magnetic field with only slight deflection. This technology helps understand how magnetic fields and quantum processes affect material electronic structure to improve quantum technology production.
The QSA team is tackling previously unsolvable problems faster by pushing fundamental physics and boosting quantum computers’ efficiency, scalability, dependability, and interaction.
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