Interfacing Superconducting Qubits With Cryogenic Logic: Readout
Interfacing Superconducting Qubits With Cryogenic Logic: Readout
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DOI：
10.1109/tasc.2019.2908884
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发表时间：
2019-08-01
影响因子：
1.8
通讯作者：
Plourde, Britton L. T.
中科院分区：
文献类型：
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作者：
Howington, Caleb;Opremcak, Alex;Plourde, Britton L. T.
随着超导量子处理器的尺寸和复杂性增加，用于量子位控制和读出的标准技术的可扩展性成为限制因素。用低温数字组件取代室温模拟组件可以实现远远超出当前最先进的具有数十个量子位的量子位阵列的系统。利用外差读出执行量子位测量的标准技术使用量子限制的低温放大器链，并且需要具有多个控制线和泵浦信号的冰箱内的庞大微波组件。此外，结果仅在室温下可在软件中访问。测量量子比特的另一种方法是将量子比特状态映射到微波腔中的光子占据，然后使用约瑟夫森光电倍增管（JPM）进行后续光子检测。JPM测量量子位并将结果存储在经典循环电流中。为了利用这一结果，我们可以利用现有的单通量量子（SFQ）电路。欠阻尼约瑟夫森传输线（JTL）可以耦合到JPM，并且根据JPM的循环电流状态，加速或延迟沿着JTL行进的通量子。然后，该通量延迟可以被转换为SFQ逻辑信号，从而产生具有近端微制造设备的数字量子比特读出，为纠错码所需的低温数字反馈铺平了道路。
As superconducting quantum processors increase in size and complexity, the scalability of standard techniques for qubit control and readout becomes a limiting factor. Replacing room temperature analog components with cryogenic digital components could allow for the realization of systems well beyond the current state-of-the-art qubit arrays with tens of qubits. The standard technique for performing a qubit measurement with heterodyne readout uses a quantum-limited cryogenic amplifier chain and requires bulky microwave components inside the refrigerator with multiple control lines and pump signals. Additionally, the result is only accessible in software at room temperature. An alternative method for measuring qubits involves mapping the qubit state onto the photon occupation in a microwave cavity, followed by subsequent photon detection using a Josephson photomultiplier (JPM). The JPM measures the qubit and stores the result in a classical circulating current. To make use of this result, we can leverage existing single flux quantum (SFQ) circuitry. An underdamped Josephson transmission line (JTL) can be coupled to the JPM and fluxons traveling along the JTL are accelerated or delayed, depending on the circulating current state of the JPM. This fluxon delay can then be converted to an SFQ logic signal resulting in a digital qubit readout with a proximal microfabricated device, paving the way for cryogenic digital feedback necessary for error-correcting codes.