Optimally preserving quantum correlations and coherence with eternally non-Markovian dynamics

Abstract

We demonstrate, both analytically and experimentally, the usefulness of non-Markovianity for preserving correlations and coherence in quantum systems. For this, we consider a broad class of qubit evolutions, having a decoherence matrix separated from zero for large times. While any such Markovian evolution leads to an exponential loss of correlations, non-Markovianity can help to preserve correlations even in the limit t → ∞. In fact, under general assumptions, eternally non-Markovian evolution naturally emerges as the one that allows for optimal preservation of quantum correlations. For covariant qubit evolutions, we also show that non-Markovianity can be used to preserve quantum coherence at all times, which is an important resource for quantum metrology. We explicitly demonstrate this effect experimentally with linear optics, by implementing the optimal non-Markovian quantum evolution.

An Exact Expression for Multidimensional Spectroscopy of a Spin‐Boson Hamiltonian

“…is the thermal distribution of the bath at a temperature  , and the dipole moment M is set to unity for simplicity. The Fourier transform of the temporal polarization P 1 (𝜔 𝜏 ) directly leads to a corresponding linear absorption spectrum: [24] A(𝜔 𝜏 ) ∝ −Re{iP 1 (𝜔 𝜏 )} (8) simulated for three representative temperatures and plotted in the top panel of Figure 1b. The absorption spectrum exhibits a complex lineshape at the lowest temperature of 10 K that becomes gradually featureless up to 70 K. Besides the sharp zerophonon line [39] (broadened by 𝛾 = 0.1 THz), the surrounding pedestal physically corresponds to inelastic scattering with lowfrequency vibrations and is therefore a direct characterization of the spectral density.…”

“…[2,3] This is driven by two primary motivations, namely that system-bath coupling is essential to understanding complex quantum systems [4,5] and that optimizing thermal decoherence is essential for quantum technologies. [6][7][8] Optical spectroscopy is perhaps the most direct way of interrogating open quantum systems. Most commonly, linear spectroscopies such as absorption or fluorescence spectroscopy [9] return spectral lineshapes that provide insight into coherence dephasing, and thereby system-bath coupling.…”

“…[ 2,3 ] This is driven by two primary motivations, namely that system‐bath coupling is essential to understanding complex quantum systems [ 4,5 ] and that optimizing thermal decoherence is essential for quantum technologies. [ 6–8 ]…”

Interplay between Non-Markovianity of Noise and Dynamics in Quantum Systems

“…Non-Markovianity has been discussed as a possible resource for quantum information tasks such as quantum system control [ 1 ], efficient entanglement distribution [ 2 ], perfect state transfer of mixed states [ 3 ], quantum channel capacity improvement [ 4 ], and efficiency of work extraction from the Otto cycle [ 5 ]. Miller et al [ 6 ] carried out an optical study of the relation between non-Markovianity and the preservation of quantum coherence and correlations, which are essential resources for quantum metrology applications. Various approaches, from environmental engineering to classical driving to controlling the non-Markovianity of quantum dynamics, have been proposed, analyzed, and experimentally realized in recent years.…”

Cohering and decohering power of massive scalar fields under instantaneous interactions

“…Coherence plays a part in other physical contexts as well, such as in quantum metrology [22,23], thermodynamics [24][25][26][27][28] and even possibly in biological processes [29,30]. Because of its usefulness as a resource, it is of particular interest to study the conditions under which coherence can be extracted or generated from other systems [31][32][33][34], as well as devise methods for its protection [35][36][37] against the decohering effects of the environment [38][39][40].…”