Abstract
We present a heralded state preparation scheme for driven nonlinear open quantum systems. The protocol is based on a continuous photon counting measurement of the system's decay channel. When no photons are detected for a period of time, the system has relaxed to a measurement-induced pseudo-steady state. We illustrate the protocol by the creation of states with a negative Wigner function in a Kerr oscillator, a system whose unconditional steady state is strictly positive.
Highlights
Nonlinearity is a crucial prerequisite for quantum algorithms to outperform their classical counterparts in quantum information processing because it gives rise to states or operations that cannot be efficiently described in a classical framework [1]
We demonstrate that quantum trajectories can continuously relax to deterministic states whose presence is revealed by the detection signal
Our results shed light on the actual dynamics of an open quantum system when the information leaking out to the environment is not discarded. They can be seen as a practical protocol for heralded state preparation in open quantum systems that is feasible with current technology
Summary
Nonlinearity is a crucial prerequisite for quantum algorithms to outperform their classical counterparts in quantum information processing because it gives rise to states or operations that cannot be efficiently described in a classical framework [1]. An important property to evaluate the usefulness of a quantum state in this context is the occurrence of negative values in its phase-space quasiprobability distribution [2,3,4] Such nonclassical states are challenging to prepare and stabilize because of unavoidable decoherence due to interaction with an unmonitored environment. We demonstrate that quantum trajectories can continuously relax to deterministic states whose presence is revealed by the detection signal This mechanism opens a new alternative path in heralded quantum state preparation and allows one to stabilize certain nonclassical states without feedback, including Schrödinger kitten states. They can be seen as a practical protocol for heralded state preparation in open quantum systems that is feasible with current technology
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