Optimal Zeno Dragging for Quantum Control: A Shortcut to Zeno with Action-based Scheduling Optimization

Kavli Affiliate: Birgitta Whaley

| First 5 Authors: Philippe Lewalle, Yipei Zhang, K. Birgitta Whaley, ,

| Summary:

The quantum Zeno effect asserts that quantum measurements inhibit
simultaneous unitary dynamics when the "collapse" events are sufficiently
strong and frequent. This applies in the limit of strong continuous measurement
or dissipation. It is possible to implement a dissipative control that is known
as "Zeno Dragging", by dynamically varying the monitored observable, and hence
also the eigenstates which are attractors under Zeno dynamics. This is similar
to adiabatic processes, in that the Zeno dragging fidelity is highest when the
rate of eigenstate change is slow compared to the measurement rate. We
demonstrate here two methods for using such dynamics to achieve control of
quantum systems. The first, which we shall refer to as "shortcut to Zeno", is
analogous to the shortcuts to adiabaticity (counterdiabatic driving) that are
frequently used to accelerate unitary adiabatic evolution. In the second
approach we apply the Chantasri Dressel Jordan (2013, CDJ) stochastic action,
and demonstrate that the extremal-probability readout paths derived from this
are well suited to setting up a Pontryagin-style optimization of the Zeno
dragging schedule. Implementing these methods on the Zeno dragging of a qubit,
we find that both approaches yield the same solution, namely, that the optimal
control is a unitary that matches the motion of the Zeno-monitored eigenstate.
These methods open up new pathways toward systematically developing dynamic
control of Zeno subspaces to realize dissipatively-stabilized quantum
operations.

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