2024/09/25 by Xianpeng Zhang, Zhang, Xian-Peng, Chuanchang Zeng +7
Computer Science · Engineering · Physics and Astronomy · #Advanced Memory and Neural Computing #FOS: Physical sciences #Quantum Computing Algorithms and Architecture #Quantum Physics (quant-ph) #Quantum and electron transport phenomena #Superconductivity (cond-mat.supr-con)
paper · pdf · doi:10.48550/arxiv.2409.17008
openalex publication_date 2024/09/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Nondemolition protocols use ancilla qubits to identify the fragile quantum state of a qubit without destroying its encoded information, thus playing a crucial role in nondestructive quantum measurements particularly relevant for quantum error correction. However, the multitude of ancilla preparations, information transfers, and ancilla measurements in these protocols create an intrinsic overhead for information processing. Here we consider an Andreev qubit defined in a quantum-dot Josephson junction and show that the macroscopic time-dependent oscillatory supercurrent arising from the quantum interference of the many-body eigenstates, can be used to probe the qubit itself-arbitrarily close to the nondestructive limit-under currently available experimental capabilities. This readout of arbitrary superposition states of Andreev qubits avoids ancillae altogether and significantly reduces experimental overhead as no repetitive qubit reinitialization is needed. Our prediction of an AC-like Josephson effect without an applied external voltage, which enables the nondestructive qubit readout, is a unique macroscopic manifestation of the microscopic dynamics of the Andreev quantum state. Our findings should have an unprecedented impact on advancing research and applications involving Andreev dots, thus positioning them as promising qubit contenders for quantum processing and technologies.