High-fidelity, multi-qubit generalized measurements with dynamic circuits

• URL: http://arxiv.org/abs/2312.14087v2
• Date: Mon, 26 Aug 2024 05:05:28 GMT
• Title: High-fidelity, multi-qubit generalized measurements with dynamic circuits
• Authors: Petr Ivashkov, Gideon Uchehara, Liang Jiang, Derek S. Wang, Alireza Seif,
• Abstract summary: Generalized measurements, also called positive operator-valued measures (POVMs), can offer advantages over projective measurements in quantum information tasks. Here, we realize a generalized measurement of one and two superconducting qubits with high fidelity and in a single experimental setting. We showcase a highly effective use of approximate compiling to enhance POVM fidelity in noisy conditions.
• Score: 1.6437645274005803
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Generalized measurements, also called positive operator-valued measures (POVMs), can offer advantages over projective measurements in various quantum information tasks. Here, we realize a generalized measurement of one and two superconducting qubits with high fidelity and in a single experimental setting. To do so, we propose a hybrid method, the "Naimark-terminated binary tree," based on a hybridization of Naimark's dilation and binary tree techniques that leverages emerging hardware capabilities for mid-circuit measurements and feed-forward control. Furthermore, we showcase a highly effective use of approximate compiling to enhance POVM fidelity in noisy conditions. We argue that our hybrid method scales better toward larger system sizes than its constituent methods and demonstrate its advantage by performing detector tomography of symmetric, informationally complete POVM (SIC-POVM). Detector fidelity is further improved through a composite error mitigation strategy that incorporates twirling and a newly devised conditional readout error mitigation. Looking forward, we expect improvements in approximate compilation and hardware noise for dynamic circuits to enable generalized measurements of larger multi-qubit POVMs on superconducting qubits.

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