利用 Quarton 耦合器实现超快超导量子比特读出
Ultrafast Superconducting Qubit Readout with the Quarton Coupler
AI总结：
本文提出利用 quarton 耦合器实现 transmon 量子比特与读出谐振器间大于 250 MHz 的交叉克尔耦合，将超导量子比特读出时间缩短至 5 ns，并保持超过 99% 的读出与 QND 保真度。
摘要：
快速、高保真且量子非破坏（QND）的量子比特读出是量子信息处理的基本要素。对于超导量子比特，最先进的读出方案基于量子比特与其读出谐振器之间的色散交叉克尔耦合。由此实现的读出可以具有高保真度和 QND 特性，但由于色散交叉克尔强度仅为 10 MHz 量级，读出时间目前被限制在 50 ns 量级。在此，我们提出一种新的读出方案，利用 quarton 耦合器在 transmon 量子比特与其读出谐振器之间实现大于 250 MHz 的大交叉克尔耦合。全主方程模拟显示，读出时间可达 5 ns，且读出保真度和 QND 保真度均超过 99%。与最先进的色散读出不同，所提出的“quartonic 读出”方案依赖于具有线性化跃迁的 transmon 作为读出谐振器。通过对耦合系统进行详细的理论处理和参数研究，我们找到了这样的工作点。quartonic 读出电路在实验上也是可行的，并且能够保持量子比特的相干特性。我们的工作揭示了一条通过工程化非线性光-物质耦合、在现有设计无法达到的参数范围内实现超导量子比特读出数量级提升的新路径。
英文摘要：
Fast, high-fidelity, and quantum nondemolition (QND) qubit readout is an essential element of quantum information processing. For superconducting qubits, state-of-the-art readout is based on a dispersive cross-Kerr coupling between a qubit and its readout resonator. The resulting readout can be high-fidelity and QND, but readout times are currently limited to the order of 50 ns due to the dispersive cross-Kerr of magnitude 10 MHz. Here, we present a new readout scheme that uses the quarton coupler to facilitate a large (greater than 250 MHz) cross-Kerr between a transmon qubit and its readout resonator. Full master equation simulations show a 5 ns readout time with greater than 99% readout and QND fidelity. Unlike state-of-the-art dispersive readout, the proposed "quartonic readout" scheme relies on a transmon with linearized transitions as the readout resonator. Such operational points are found from a detailed theoretical treatment and parameter study of the coupled system. The quartonic readout circuit is also experimentally feasible and preserves the coherence properties of the qubit. Our work reveals a new path for order-of-magnitude improvements of superconducting qubit readout by engineering nonlinear light-matter couplings in parameter regimes unreachable by existing designs.
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