Decoherence in models for hard-core bosons coupled to optical phonons

Abstract

Understanding coherent dynamics of excitons, spins, or hard-core bosons (HCBs) has tremendous scientific and technological implications for light harvesting and quantum computation. Here, we study decay of excited-state population and decoherence in two models for HCBs, namely: an infinite-range HCB model governed by Markovian dynamics and a two-site HCB model with sitedependent strong potentials and subject to non-Markovian dynamics. Both models are investigated in the regimes of antiadiabaticity and strong HCB-phonon coupling with each site providing a different local optical phonon environment; furthermore, the HCB systems in both models are taken to be initially uncorrelated with the environment in the polaronic frame of reference. For the infinite-range model, we derive an effective many-body Hamiltonian that commutes with the long-range system Hamiltonian and thus has the same set of eigenstates; consequently, a quantummaster-equation approach shows that the quantum states of the system do not decohere. In the case of the two-site HCB model, we show clearly that the degree of decoherence and decay of excited state are enhanced by the proximity of the site-energy difference to the eigenenergy of phonons and are most pronounced when the site-energy difference is at resonance with twice the polaronic energy; additionally, the decoherence and the decay effects are reduced when the strength of HCB-phonon coupling is increased. Even for a multimode situation, the degree of decoherence and decay are again dictated by the nearness of the energy difference to the allowed phonon mode eigenenergies. PACS numbers: 71.38.-k, 03.65.Yz, 85.35.Be, 87.10.HkWe choose the basis {|10 , |01 } for our analysis and obtain the following useful expressions: e −iH L s t |10 = [p(t) * |10 − iκq(t)|01 ]e i J 4 t , (48) and

Experimental signature of collective enhancement in nuclear level density

“…The estimated deformation from the two GDR peaks is β = 0.32 similar to the ground state deformation of Tm nuclei [30]. The bremsstrahlung component, as measured and observed in our earlier experiments at similar beam energy [36,49], was parameterized by an exponential function (e −Eγ /E0 ) where the slope parameter E 0 was chosen according to the bremsstrahlung systematics [50]. Inter-Energy (MeV) estingly, the enhancement factor used for 168 Tm to describe the neutron spectrum, simultaneously explains the γ spectrum between E γ = 7 and 11 MeV.…”

“…Thus, almost similar enhancement was required in the level density of both 168 Tm and 169 Tm to simultaneously explain the neutron and the GDR spectra. It is also very interesting to note that no such enhancement in the γ spectra was observed in our earlier experiments at similar excitation energies for near spherical nuclei 97 Tc [36], 119 Sb [49], and 201 Tl [35]. It needs to be mentioned here that a similar enhancement in NLD was observed in the proton decay from 104 Pd but at much lower effective excitation energy (below 6 MeV) [51].…”

“…1. The details of the GDR [34][35][36][37] and the neutron analyses [25,26,38] have already been discussed in our earlier papers.…”

Decoherence dynamics of interacting qubits coupled to a bath of local optical phonons

“…a system with two hardcore bosons is reported by authors in Ref. 47. In this work, we consider the extreme case of distance independent interaction among the spins, i.e., the IRHM.…”

Angular analyses of exclusive B¯→XJℓ1Dey 2017Phys. Rev. D4040View full textAdd to dashboardCite

“…The goal of this paper is lay out the formalism for performing angular analyses incorporating these higher spin states, from an experimentalist's perspective. The spin J ≤ 2 case was addressed in a previous work [2] and subsequently employed to to analyze LHCb Run I [3] data in the B 0 → K − π + µ − µ + mode, with q 2 ∈ [1.1, 6.0] GeV 2 and m Kπ ∈ [1330, 1530] MeV, where S-, P -and D-waves occur in the [Kπ] system. Here q 2 is the invariant di-lepton mass.…”