Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 68, Number 7
Monday–Friday, June 5–9, 2023; Spokane, Washington
Session X04: Focus Session: Novel Approaches in Error CorrectionFocus Live Streamed
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Chair: Jeff Thompson, Princeton University Room: Conference Theater |
Friday, June 9, 2023 8:00AM - 8:30AM |
X04.00001: Hardware-Aware Quantum Error Correction Invited Speaker: Liang Jiang To effectively suppress practical imperfections, we aim to design quantum error correction schemes that can suppress dominant errors and enhance performance for specific hardware. In this talk, I will discuss how to design quantum error correcting codes that can optimally suppress practically-relevant errors. Furthermore, I will provide examples of custom-designed quantum error correction schemes that can efficiently suppress practically-relevant errors in AMO and solid-state systems. |
Friday, June 9, 2023 8:30AM - 8:42AM |
X04.00002: Relaxational Quantum Eigensolver: State Characterization and Thermometry Alexandar M Liguori-Schremp, George S Grattan, Eliot Kapit, Peter Graf, David Rodriguez Perez Many quantum algorithms, such as QAOA or the Variational Quantum Eigensolver (VQE), focus on minimizing a classical or quantum problem Hamiltonian through adiabatic preparation-like ansatze. However, these algorithms typically must race against proliferating gate error, limiting their usefulness for problems needing high circuit depths. Drawing on ideas from bath engineering, open quantum systems, and variational algorithms, we develop an algorithm exhibiting continuous, approximate error correction, which we call the Relaxational Quantum Eigensolver (RQE). In RQE, we weakly couple a second register of auxiliary "shadow" qubits to the primary system in Trotterized evolution, thus engineering an approximate zero-temperature bath by periodically resetting the auxiliary qubits during the algorithm's runtime. Balancing the infinite temperature bath of random gate error, RQE returns states with an average energy equal to a constant fraction of the ground state. In this work we focus on better understanding the steady state, its "temperature" T as a function of error rate, and methods for estimating both T and deviations from thermal behavior. This basic proof of concept demonstrates stabilization of finite temperature states of many-body Hamiltonians against random error. |
Friday, June 9, 2023 8:42AM - 8:54AM |
X04.00003: Encoding a Qubit in a Qudit for fault tolerant quantum computation Sivaprasad T Omanakuttan, Vikas V Buchemmavari, Jonathan A Gross, Milad Marvian Mashhad, Ivan H Deutsch We construct a class of quantum error-correcting cat codes for atomic spin systems, similar in spirit to the cat codes used for a bosonic mode, by encoding a logical qubit in a spin qudit. We study how a repetition code based on the cat codes in the spin systems can be used for fault-tolerant quantum computation and we develop a universal set of gates that respects the error set. One key ingredient is the development of a bias-preserving CNOT gate protocol suitable for errors in the spins systems. Using the well-known Rydberg blockade for entanglement in neutral atom quantum computing, we construct a bias-preserving CNOT gate. We categorize the errors as phase errors and amplitude errors. The phase errors are analogous to phase-flip errors for qubits and can be corrected in a similar way by constructively measuring the syndrome followed by an X-gate. To correct amplitude errors, we use the higher dimensional nature of the qudit, couple the data qubits with ancilla, and use a swap gate to swap the states. Following this, a destructive measurement of the data qubits determines the syndrome for amplitude errors. We also study the fault-tolerant threshold for error correction by studying the errors on the CNOT gates; the thresholds are close to the error-biased cat qubits [1]. Thus, our results provide a path to fault tolerance with fewer qubits by using the extra available internal degrees of freedom in atoms. |
Friday, June 9, 2023 8:54AM - 9:06AM |
X04.00004: Non-destructive mid-circuit measurements on a neutral atom quantum processor Trent Graham, Linipun Phuttitarn, Ravikumar Chinnarasu, Yunheung Song, Cody Poole, Kais Jooya, Jacob Scott, Patrick Eichler, Abraham Scott, Mark Saffman Quantum bits are sensitive to the external environment and have a limited coherence time. Quantum error correction can mitigate this degradation by combining mid-circuit measurements of ancilla qubits with corrective operations that are conditioned on the results of measurement outcomes. However, conventional state measurement protocols for neutral atom qubits in an optical lattice are not compatible with mid-circuit measurement since they are global and destructive. |
Friday, June 9, 2023 9:06AM - 9:18AM |
X04.00005: Fault-Tolerant Connection of Error-Corrected Qubits with Noisy Links Josiah J Sinclair, Joshua Ramette, Nikolas P Breuckmann, Vladan Vuletic One of the most promising routes toward scalable quantum computing is a modular approach. We show that distinct surface code patches can be connected in a fault-tolerant manner even in the presence of substantial noise along their connecting interface. We quantify analytically and numerically the combined effect of errors across the interface and bulk. We show that the system can tolerate 14 times higher noise at the interface compared to the bulk, with only a small effect on the code's threshold and sub-threshold behavior, reaching threshold with ~1% bulk errors and ~10% interface errors. This implies that fault-tolerant scaling of error-corrected modular devices is within reach using existing technology. |
Friday, June 9, 2023 9:18AM - 9:30AM |
X04.00006: Optimizing Rydberg Gates for Logical Qubit Performance Sven Jandura, Jeff D Thompson, Guido Pupillo Improving the fidelity of two-qubit Rydberg blockade gates is one of the key challenges for the continued development of neutral atom quantum processors. Here, we employ quantum optimal control methods to construct a family of Rydberg blockade gates that are robust against two common, major imperfections: intensity inhomogeneity and Doppler shifts. These gates can be implemented with a global laser pulse, whose phase is modulated in time to achieve the desired robustness. While being robust against intensity inhomogeneity and Doppler shifts, the gates show an increased susceptibility to Rydberg decay errors. To quantify this tradeoff, we evaluate the gate fidelity for the example of erasure-biased metastable 171Yb qubits, and find that the robust gates significantly outperform existing gates for moderate or large imperfections. We then consider the logical performance of these gates in the context of an error correction code. In this case, we observe that the robust gates outperform existing gates even for very small imperfections, because they maintain the native large bias towards erasure errors. Our results significantly reduce the laser stability and atomic temperature requirements to achieve fault-tolerant quantum computing with neutral atoms. |
Friday, June 9, 2023 9:30AM - 10:00AM |
X04.00007: Quantum error correction with motional states of trapped ions Invited Speaker: Jonathan Home I will describe experimental progress aimed at realizing error-corrected quantum computing systems in the motional degree of freedom of trapped-atomic ions. We have realized many rounds of quantum error correction in GKP-encoded logical qubits, extending the logical qubit lifetime by more than a factor of 3 [1,2]. Critical to these experiments was the implementation of measurement and correction suited to experimentally accessible finite-energy states. I will present theoretical and experimental progress towards implementing multi-qubit gates in a radio-frequency trap. Furthermore, I will discuss possibilities to extend control of ions to microtrap arrays using micro-fabricated Penning traps [3], based on our recent first trapping and motional state control in such a setup. |
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