美国耶鲁大学Devoret, Michel H.团队近日研究了盈亏平衡点以外的量子误差校正。该项研究成果发表在2025年5月14日出版的《自然》上。

Hilbert空间维数是量子信息处理的关键资源。大的整体Hilbert空间不仅是量子纠错的基本要求，而且大的局部Hilbert空间也有利于更有效地实现门和算法。因此，近年来，人们在使用qudits（d > 2的d维量子系统）开发量子计算平台方面进行了大量的实验工作，qudits可作为量子信息的基本单位。与量子比特一样，从长远来看，对这些量子比特的量子纠错是必要的，但到目前为止，逻辑量子比特的纠错还没有得到实验证明。 

研究组报道了纠错逻辑qutrit（d = 3）和ququart（d = 4）的实验实现，这是通过Gottesman–Kitaev–Preskill玻色子密码实现的。使用强化学习代理，研究组优化了Gottesman–Kitaev–Preskill qutrit（ququart）作为三元（四元）量子存储器，并实现了超过盈亏平衡的纠错，增益为1.82 ± 0.03 (1.87 ± 0.03）。这项工作代表了一种利用谐振子的大Hilbert空间来实现硬件高效量子纠错的新方法。

附：英文原文

Title: Quantum error correction of qudits beyond break-even

Author: Brock, Benjamin L., Singh, Shraddha, Eickbusch, Alec, Sivak, Volodymyr V., Ding, Andy Z., Frunzio, Luigi, Girvin, Steven M., Devoret, Michel H.

Issue&Volume: 2025-05-14

Abstract: Hilbert space dimension is a key resource for quantum information processing1,2. Not only is a large overall Hilbert space an essential requirement for quantum error correction, but a large local Hilbert space can also be advantageous for realizing gates and algorithms more efficiently3,4,5,6,7. As a result, there has been considerable experimental effort in recent years to develop quantum computing platforms using qudits (d-dimensional quantum systems with d>2) as the fundamental unit of quantum information8,9,10,11,12,13,14,15,16,17,18,19. Just as with qubits, quantum error correction of these qudits will be necessary in the long run, but so far, error correction of logical qudits has not been demonstrated experimentally. Here we report the experimental realization of an error-corrected logical qutrit (d=3) and ququart (d=4), which was achieved with the Gottesman–Kitaev–Preskill bosonic code20. Using a reinforcement learning agent21,22, we optimized the Gottesman–Kitaev–Preskill qutrit (ququart) as a ternary (quaternary) quantum memory and achieved beyond break-even error correction with a gain of 1.82±0.03 (1.87±0.03). This work represents a novel way of leveraging the large Hilbert space of a harmonic oscillator to realize hardware-efficient quantum error correction.

DOI: 10.1038/s41586-025-08899-y

Source: https://www.nature.com/articles/s41586-025-08899-y