Quantum trajectory analysis of single microwave photon detection by nanocalorimetry

基于冷里德伯气体翻转轨迹的量子增强计量学

Quantum enhanced metrology based on flipping trajectory of cold Rydberg gases

本研究在冷原子系统中实验实现基于冷里德伯气体翻转轨迹的量子增强计量学，测得等效灵敏度1.6(5) nV cm⁻¹ Hz⁻¹/²，为传感计量应用提供新方法。

Observing and Verifying the Quantum Trajectory of a Mechanical Resonator

Continuous weak measurement allows localizing open quantum systems in state space, and tracing out their quantum trajectory as they evolve in time. Efficient quantum measurement schemes have previously enabled recording quantum trajectories of microwave photon and qubit states. We apply these concepts to a macroscopic mechanical resonator, and follow the quantum trajectory of its motional state conditioned on a continuous optical measurement record. Starting with a thermal mixture, we eventually obtain coherent states of 78% purity--comparable to a displaced thermal state of occupation 0.14. W…

Superconductor Qubits Hamiltonian Approximations Effect on Quantum State Evolution and Control

Quantum state on Bloch sphere for superconducting charge qubit, phase qubit and flux qubit for all time in absence of external drive is stable to initial state. By driving the qubits, approximation of charge and flux Hamiltonian lead to quantum state rotation in Bloch sphere around an axis completely differ from rotation vector of exact Hamiltonian. The trajectory of quantum state for phase qubit for approximated and exact Hamiltonian is the same but the expectation of quantum observable has considerable errors as two other qubits. microwave drive control is designed for approximated Hamiltoni…

Quantum estimation of a time dependent perturbation

We analyze the estimation of a time dependent perturbation acting on a continuously monitored quantum system. We describe the temporal fluctuations of the perturbation by a Hidden Markov Model, and we combine quantum measurement theory and classical filter theory into a time evolving hybrid quantum and classical trajectory. The forward-backward analysis that permits smoothed estimates of classical Hidden Markov Models has a counterpart in the theory of retrodiction and Past Quantum States. As a specific example, we apply our hybrid trajectory and Past Quantum State theory to the sensing of a f…

Synchronization of a superconducting qubit to an optical field mediated by a mechanical resonator

We study the synchronization of a superconducting qubit to an external optical field via a mechanical resonator in a hybrid optoelectromechanical system. The quantum trajectory method is employed to investigate synchronization. The bistability in one of the qubit polarization vectors, where the qubit rotates about the polarization vector, is observed for a single quantum trajectory run. The rotation in one of the stable states is synced with the external optical drive. When the number of trajectories is significantly increased, the qubit no longer displays bistability. However, synchronization…

Manipulating the shape of electronic non-dispersive wave-packets in the hydrogen atom: numerical tests in realistic experimental conditions

We show that combination of a linearly polarized resonant microwave field and a parallel static electric field may be used to create a non-dispersive electronic wavepacket in Rydberg atoms. The static electric field allows for manipulation of the shape of the elliptical trajectory the wavepacket is propagating on. Exact quantum numerical calculations for realistic experimental parameters show that the wavepacket evolving on a linear orbit can be very easily prepared in a laboratory either by a direct optical excitation or by preparing an atom in an extremal Stark state and then slowly switchin…