Exploring More-Coherent Quantum Annealing

Abstract

In the quest to reboot computing, quantum annealing (QA) is an interesting candidate for a new capability. While it has not demonstrated an advantage over classical computing on a real-world application, many important regions of the QA design space have yet to be explored. In IARPA's Quantum Enhanced Optimization (QEO) program, we have opened some new lines of inquiry to get to the heart of QA, and are designing testbed superconducting circuits and conducting key experiments. In this paper, we discuss recent experimental progress related to one of the key design dimensions: qubit coherence. Using MIT Lincoln Laboratory's qubit fabrication process and extending recent progress in flux qubits, we are implementing and measuring QA-capable flux qubits. Achieving high coherence in a QA context presents significant new engineering challenges. We report on techniques and preliminary measurement results addressing two of the challenges: crosstalk calibration and qubit readout. This groundwork enables exploration of other promising features and provides a path to understanding the physics and the viability of quantum annealing as a computing resource.

arXiv comment7 pages, 3 figures. Accepted by the 2018 IEEE International Conference on Rebooting Computing (ICRC)

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• The squeezed Kerr oscillator: spectral kissing and phase-flip robustness
• Calibration of flux crosstalk in large-scale flux-tunable superconducting quantum circuits
• Continuous quantum error correction for evolution under time-dependent Hamiltonians
• A double-slit proposal for quantum annealing
• Customized quantum annealing schedules
• Anneal-path correction in flux qubits
• Enhancing quantum annealing performance by a degenerate two-level system
• Demonstration of long-range correlations via susceptibility measurements in a one-dimensional superconducting Josephson spin chain
• Dissipative Landau-Zener tunneling in the crossover regime from weak to strong environment coupling
• Excited state search using quantum annealing
• Quantum adiabatic theorem for unbounded Hamiltonians with a cutoff and its application to superconducting circuits
• Decoherence of a tunable capacitively shunted flux qubit
• Benchmarking Embedded Chain Breaking in Quantum Annealing