Optimal control in large open quantum systems: the case of transmon readout and reset

• URL: http://arxiv.org/abs/2403.14765v3
• Date: Thu, 20 Feb 2025 18:00:36 GMT
• Title: Optimal control in large open quantum systems: the case of transmon readout and reset
• Authors: Ronan Gautier, Élie Genois, Alexandre Blais,
• Abstract summary: We present a framework that combines the adjoint-state method together with reverse-time backpropagation to solve prohibitively large open-system quantum control problems. We apply this framework to optimize two inherently dissipative operations in superconducting qubits. Our results show that while standard pulses for dispersive readout are nearly optimal, adding a transmon drive during the protocol can yield 2x improvements in fidelity and duration.
• Score: 44.99833362998488
• License:
• Abstract: We present a framework that combines the adjoint-state method together with reverse-time backpropagation to solve prohibitively large open-system quantum control problems. Our approach enables the optimization of arbitrary cost functions with fully general controls applied on large open quantum systems described by a Lindblad master equation. It is scalable, computationally efficient, and has a low-memory footprint. We apply this framework to optimize two inherently dissipative operations in superconducting qubits which lag behind in terms of fidelity and duration compared to other unitary operations: the dispersive readout and all-microwave reset of a transmon qubit. Our results show that while standard pulses for dispersive readout are nearly optimal, adding a transmon drive during the protocol can yield 2x improvements in fidelity and duration. We further demonstrate a 2x improvement in reset fidelity and duration through pulse shaping, indicating significant potential for enhancement in reset protocols. Our approach can readily be applied to optimize quantum controls in a vast range of applications such as reservoir engineering, autonomous quantum error correction, and leakage-reduction units.

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