Abstract
Quantum discrimination and estimation are pivotal for many quantum technologies, and their performance depends on the optimal choice of probe state and measurement. Here we show that their performance can be further improved by suitably tailoring the pulses that make up the interferometer. Developing an optimal control framework and applying it to the discrimination and estimation of a magnetic field in the presence of noise, we find an increase in the overall achievable state distinguishability. Moreover, the maximum distinguishability can be stabilized for times that are more than an order of magnitude longer than the decoherence time.
Highlights
Quantum control has become a very versatile tool for quantum technologies [1,2], including quantum computation [3,4,5,6] and quantum simulation [7,8]
Developing an optimal control framework and applying it to the discrimination and estimation of a magnetic field in the presence of noise, we find an increase in the overall achievable state distinguishability
For a control problem where an initial state should be transferred into a given target state, it is determined by the general speed of the evolution, typically set by the Hamiltonian, and the distance between initial and target state
Summary
Quantum control has become a very versatile tool for quantum technologies [1,2], including quantum computation [3,4,5,6] and quantum simulation [7,8]. We use quantum optimal control to maximize the distance between the two states by shaping the external fields that make up the interferometer This can be understood as tailoring the external field to drive the states evolving under different dynamics away from each other, instead of toward a common target. Since both states depend on the control, the distance between them is typically not a linear function, which is different from the case of a fixed target. Krotov’s method for quantum optimal control [10,11] can be used in such a case We employ it here to optimize discrimination and estimation of a magnetic field in the presence of noise, increasing the performance compared to the standard scheme based on a Ramsey interferometer.
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