Quantum Zeno phenomena: pulsed versus continuous measurement

Steering Distillation by "Pulsed" and "Continuous" Measurements

A new systematic strategy for steering the distillation process for a quantum system, that utilizes the so-called "pulsed" and "continuous" measurements on another quantum system in interaction with the former, is proposed. The distillation process characterized by the specific interaction between the two systems and the "pulsed" measurements is shown to be controllable through the "continuous" measurements, i.e., the quantum Zeno dynamics, providing an effective recipe to prefix the target.

教程：理解量子芝诺与反芝诺区域

Tutorial: Understanding quantum Zeno and anti-Zeno regimes

本教程通过受驱动量子比特的示例，统一阐释量子芝诺与反芝诺效应的机制，适合量子控制、测量及量子计算领域的研究者学习应用。

Quantum state driving: measurements versus pulses

The quantum Zeno effect is well-known for fixing a system to an eigenstate by frequent measurements. It is also known that applying frequent unitary pulses induces a Zeno subspace that can also pin the system to an eigenspace. Both approaches have been studied as means to maintain a system in a certain subspace. Extending the two concepts, we consider making the measurements/pulses dynamical so that the state can move with the motion of the measurement axis/pulse basis. We show that the system stays in the dynamical eigenbasis when the measurements/pulses are slowly changing. Explicit bounds f…

Quantum Zeno Dynamics from General Quantum Operations

We consider the evolution of an arbitrary quantum dynamical semigroup of a finite-dimensional quantum system under frequent kicks, where each kick is a generic quantum operation. We develop a generalization of the Baker-Campbell-Hausdorff formula allowing to reformulate such pulsed dynamics as a continuous one. This reveals an adiabatic evolution. We obtain a general type of quantum Zeno dynamics, which unifies all known manifestations in the literature as well as describing new types.

零点阻塞实现光子量子优化

Zeno Blockade Enabling Photonic Quantum Optimization

本文提出利用非线性光学中的零点效应实现光子量子优化，通过线性协议寻找加权最大独立集，探讨了其作为熵计算范式或量子退火在受限子空间中的应用。

Quantum Zeno Effect with the Feynman-Mensky Path-Integral Approach

A model for quantum Zeno effect based upon an effective Schrödinger equation originated by the path-integral approach is developed and applied to a two-level system simultaneously stimulated by a resonant perturbation. It is shown that inhibition of stimulated transitions between the two levels appears as a consequence of the influence of the meter whenever measurements of energy, either continuous or pulsed, are performed at quantum level of sensitivity. The generality of this approach allows to qualitatively understand the inhibition of spontaneous transitions as the decay of unstable partic…

受相干控制的量子泽诺动力学从精确重置映射

Coherence-Controlled Quantum Zeno Dynamics from Exact Reset Maps

本文提出了一种精确框架，用于研究开放系统中的量子泽诺和反泽诺动力学，通过单粒子密度矩阵层面的精确闪烁重置方案，探讨了重复交互和演化的相关协议对相干保留与消除的影响。

New insights of quantum Zeno phenomenon: an indirect correlation effect among subsystems

Frequent Measurements on an unstable particle located at observable initial state freeze the particle on this state, known as quantum Zeno effect [1-14]. Measurements on an observable subspace further open the prelude of quantum Zeno dynamics [15-17]. These phenomena affect the results of quantum measurement that has been widely used in quantum information and quantum computation [18-21]. However, this common argument is insufficient when the initial state is coupled with a continuum reservoir. In such an irreversible system, intrinsic decay property destroys the frozen behavior. Although it h…

Pulsed and continuous measurements of exponentially decaying systems

We study the influence of a detector on the decay law of a quantum state whose "undisturbed" survival probability is purely exponential. In particular, we consider a detector with a finite energy band of detection, i.e. it interacts only with decay products having an energy within a certain range of values. In one case, we assume that the detector performs many repeated measurements at short time intervals in all of which a collapse of the wave function occurs (bang-bang or pulsed-type measurements). In the second case, we assume a continuous measurement which preserves unitarity. We confirm t…

Quantum time-of-flight measurements: kick clock versus continuous clock

The measurement of time durations or instants of ocurrence of events has been frequently modelled ``operationally'' by coupling the system of interest to a ``clock''. According to several of these models the operational approach is limited at low energies because the perturbation of the clock does not allow to reproduce accurately the corresponding ideal time quantity, defined for the system in isolation. We show that, for a time-of-flight measurement model that can be set to measure dwell or arrival times, these limitations may be overcome by extending the range of energies where the clock wo…

光学功率受限条件下连续与脉冲氮空位直流磁测量的比较

Comparing continuous and pulsed nitrogen-vacancy DC magnetometry in the optical-power-limited regime

本研究在光学功率受限条件下比较了连续波与脉冲NV磁测量技术，开发了包含不完全自旋极化的理论模型，发现脉冲操作灵敏度增益约2-3倍，为实际传感器开发提供协议选择指导。

Influence of the measurement on the decay law: the bang-bang case

After reviewing the description of an unstable state in the framework of nonrelativistic Quantum Mechanics (QM) and relativistic Quantum Field Theory (QFT), we consider the effect of pulsed, ideal measurements repeated at equal time intervals on the lifetime of an unstable system. In particular, we investigate the case in which the `bare' survival probability is an exact exponential (a very good approximation in both QM and QFT), but the measurement apparatus can detect the decay products only in a certain energy range. We show that the Quantum Zeno Effect can occur in this framework as well.

Longitudinal and transversal spin dynamics of donor-bound electrons in fluorine-doped ZnSe: spin inertia versus Hanle effect

The spin dynamics of the strongly localized, donor-bound electrons in fluorine-doped ZnSe epilayers is studied by pump-probe Kerr rotation techniques. A method exploiting the spin inertia is developed and used to measure the longitudinal spin relaxation time, $T_1$, in a wide range of magnetic fields, temperatures, and pump densities. The $T_1$ time of the donor-bound electron spin of about 1.6 $μ$s remains nearly constant for external magnetic fields varied from zero up to 2.5 T (Faraday geometry) and in a temperature range $1.8-45$ K. The inhomogeneous spin dephasing time, $T_2^*=8-33$ ns, i…

Phononic bandgap nano-acoustic cavity with ultralong phonon lifetime

We present measurements at millikelvin temperatures of the microwave-frequency acoustic properties of a crystalline silicon nanobeam cavity incorporating a phononic bandgap clamping structure for acoustic confinement. Utilizing pulsed laser light to excite a co-localized optical mode of the nanobeam cavity, we measure the dynamics of cavity acoustic modes with single-phonon sensitivity. Energy ringdown measurements for the fundamental $5$~GHz acoustic mode of the cavity shows an exponential increase in phonon lifetime versus number of periods in the phononic bandgap shield, increasing up to $τ…