Zeno and anti-Zeno effects for photon polarization dephasing

Abstract

We discuss a simple, experimentally feasible scheme, which elucidates the principles of controlling ("engineering") the reservoir spectrum and the spectral broadening incurred by repeated measurements. This control can yield either the inhibition (Zeno effect) or the acceleration (anti-Zeno effect) of the quasi-exponential decay of the observed state by means of frequent measurements. In the discussed scheme, a photon is bouncing back and forth between two perfect mirrors, each time passing a polarization rotator. The horizontal and vertical polarizations can be viewed as analogs of an excited and a ground state of a two level system (TLS). A polarization beam splitter and an absorber for the vertically polarized photon are inserted between the mirrors, and effect measurements of the polarization. The polarization angle acquired in the electrooptic polarization rotator can fluctuate randomly, e.g., via noisy modulation. In the absence of an absorber the polarization randomization corresponds to TLS decay into an infinite-temperature reservoir. The non-Markovian nature of the decay stems from the many round-trips required for the randomization. We consider the influence of the polarization measurements by the absorber on this non-Markovian decay, and develop a theory of the Zeno and anti-Zeno effects in this system.

Quantum Sensing of Noisy and Complex Systems under Dynamical Control

“…The dynamical control of this multipartite system then becomes similar to single-qubit level modulation [56,[60][61][62] ( Figure 3). In frequency space, the probes are resonantly coupled by a fermionic-mode of the channel whose energy is defined to be the energy origin (zero).…”

“…This diagnostics is again based on Equation (14), the KK universal formula [44][45][46]50,55,56,[60][61][62]. Even if the ultimate goal of any modulation scheme is to reduce, or, if possible, eliminate the decoherence, one must first know the probe-bath coupling spectra so as to obtain the optimal modulation using BOTOC [34,35].…”

“…Such quasi-reversible dynamics is manifest by the quantum Zeno or anti-Zeno effects (QZE or AZE, respectively) [44][45][46][47][48][49][54][55][56][57][58][59][60][61][62][63]. The QZE and AZE correspond to the suppression and enhancement, respectively, of the bath effects via control.…”

“…Instead, here we resort to the BOTOC approach outlined above [34,35], subject to minimal-energy constraints, so as to deduce the optimal, energy-constrained control of a decohering qubit probe by modulation, for any given bath-coupling spectrum. This is achieved by controlling the decoherence rate, R(t), given a bath-coupling spectrum, G(ω), through the optimal phase modulation, ε(t) = e iφ(t) , according to the KK formula [44][45][46]50,55,56,[60][61][62] of Equation (14), under the Euler-Lagrange optimization method subject to constraints such as the minimization of the total control energy,…”

“…This is achieved by controlling the decoherence rate, ( ), given a bath-coupling spectrum, ( ) , through the optimal phase modulation, ( ) = ( ) , according to the KK formula [44][45][46]50,55,56,[60][61][62] of Equation (14), under the Euler-Lagrange optimization method subject to constraints such as the minimization of the total control energy, …”