Optimized trajectory unraveling for classical simulation of noisy quantum dynamics

Abstract

The dynamics of open quantum systems can be simulated by unraveling it into an ensemble of pure state trajectories undergoing non-unitary monitored evolution, which has recently been shown to undergo measurement-induced entanglement phase transition. Here, we show that, for an arbitrary decoherence channel, one can optimize the unraveling scheme to lower the threshold for entanglement phase transition, thereby enabling efficient classical simulation of the open dynamics for a broader range of decoherence rates. Taking noisy random unitary circuits as a paradigmatic example, we analytically derive the optimum unraveling basis that on average minimizes the threshold. Moreover, we present a heuristic algorithm that adaptively optimizes the unraveling basis for given noise channels, also significantly extending the simulatable regime. When applied to noisy Hamiltonian dynamics, the heuristic approach indeed extends the regime of efficient classical simulation based on matrix product states beyond conventional quantum trajectory methods. Finally, we assess the possibility of using a quasi-local unraveling, which involves multiple qubits and time steps, to efficiently simulate open systems with an arbitrarily small but finite decoherence rate.

5+12 pages, 4+8 figures, 0+3 tables

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Cited by in corpus (8)

• Non-unitarity maximizing unraveling of open quantum dynamics
• Large-scale stochastic simulation of open quantum systems
• Emergent unitary designs for encoded qubits from coherent errors and syndrome measurements
• Analog simulation of noisy quantum circuits
• Gauge-Fixing Quantum Density Operators At Scale
• Gauge freedoms in unravelled quantum dynamics: When do different continuous measurements yield identical quantum trajectories?
• Noisy Monitored Quantum Circuits
• Classical simulation of noisy quantum circuits via locally entanglement-optimal unravelings