Squeezing dynamics of a nanowire system with spin-orbit interaction (original) (raw)
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Achieving spin-squeezed states by quench dynamics in a quantum chain
Physical Review B, 2022
We study the time evolution of spin squeezing in the one-dimensional spin-1/2 XY model with a transverse magnetic field subject to a sudden quantum quench. The initial state is selected from the ground state phase diagram of the model, consisting of ferro-and paramagnetic phases separated by a critical value of the transverse field. Our analysis, based on exact results for the model, reveals that by a proper choice of protocol, a quantum quench from an unsqueezed state can create spin squeezed nonequilibrium states. Moreover, we identify two types of nonanalyticities in the parameter which measures the amount of spin squeezing in the system: one in its time-dependence, the other in its long-time average with the transverse field as control parameter. We argue that the first type of nonanalyticity signals an unconventional nonequilibrium quantum phase transition, appearing at certain critical times when the direction of spin squeezing suddenly changes.
Competing Effects of Interactions and Spin-Orbit Coupling in a Quantum Wire
Physical Review Letters, 2005
We study the interplay of electron-electron interactions and Rashba spin-orbit coupling in onedimensional ballistic wires. Using the renormalization group approach we construct the phase diagram in terms of Rashba coupling, Tomonaga-Luttinger stiffness and backward scattering strength. We identify the parameter regimes with a dynamically generated spin gap and show where the Luttinger liquid prevails. We also discuss the consequences for the operation of the Datta-Das transistor.
This paper reviews quantum spin squeezing, which characterizes the sensitivity of a state with respect to SU(2) rotations, and is significant for both entanglement detection and high-precision metrology. We first present various definitions of spin squeezing parameters, explain their origin and properties for typical states, and then discuss spinsqueezed states produced with nonlinear twisting Hamiltonians. Afterward, we explain pairwise correlations and entanglement in spin-squeezed states, as well as the relations between spin squeezing and quantum Fisher information, where the latter plays a central role in quantum metrology. We also review the applications of spin squeezing for detecting quantum chaos and quantum phase transitions, as well as the influence of decoherence on spin squeezing. Finally, we review several experimental realizations of spin squeezing, as well as their corresponding theoretical backgrounds, including: producing spin-squeezed states via particle collisions in Bose-Einstein condensates, transferring photon squeezing to atomic ensembles, and generating spin squeezing via quantum nondemolition measurements.
Interaction effects in a microscopic quantum wire model with strong spin–orbit interaction
New Journal of Physics, 2017
We investigate the effect of strong interactions on the spectral properties of quantum wires with strong Rashba spin-orbit (SO) interaction in a magnetic field, using a combination of matrix product state and bosonization techniques. Quantum wires with strong Rashba SO interaction and magnetic field exhibit a partial gap in one-half of the conducting modes. Such systems have attracted widespread experimental and theoretical attention due to their unusual physical properties, among which are spin-dependent transport, or a topological superconducting phase when under the proximity effect of an s-wave superconductor. As a microscopic model for the quantum wire we study an extended Hubbard model with SO interaction and Zeeman field. We obtain spin resolved spectral densities from the real-time evolution of excitations, and calculate the phase diagram. We find that interactions increase the pseudo gap at k=0 and thus also enhance the Majorana-supporting phase and stabilize the helical spin order. Furthermore, we calculate the optical conductivity and compare it with the low energy spiral Luttinger liquid result, obtained from field theoretical calculations. With interactions, the optical conductivity is dominated by an excotic excitation of a bound soliton-antisoliton pair known as a breather state. We visualize the oscillating motion of the breather state, which could provide the route to their experimental detection in e.g. cold atom experiments.
Spin squeezing in open Heisenberg spin chains
arXiv (Cornell University), 2023
Spin squeezing protocols successfully generate entangled many-body quantum states, the key pillars of the second quantum revolution. In our recent work [Phys. Rev. Lett. 129, 090403 (2022)] we showed that spin squeezing described by the one-axis twisting model can be generated in the Heisenberg spin-1/2 chain with periodic boundary conditions when accompanied by a positiondependent spin-flip coupling induced by a single laser field. In this work, we show analytically that the change of boundary conditions from the periodic to the open ones significantly modifies spin squeezing dynamics. A broad family of twisting models can be simulated by the system in the weak coupling regime, including the one-and two-axis twisting under specific conditions, providing the Heisenberg level of squeezing and acceleration of the dynamics. Our analytical findings are confirmed by full numerical simulations.
Spin squeezing in the presence of dissipation
Physics Letters A, 2009
ABSTRACT The transfer of spin between photons and localized atomic levels, for a chain of two-level atoms, is studied. The Hamiltonian of the system is modelled by a radiation term and by atom–atom and radiation-atom interactions. Effects due to dissipation are accounted for by atom-photon exchange-interactions of complex strength. It is found that the spin-squeezing is suppressed by dissipation. Calculations are performed for arrays of Rb atoms excited by a GaAlAs laser.
Spin-orbit induced spin-qubit control in nanowires
Journal of Physics: Conference Series, 2007
We elaborate on a number of issues concerning our recent proposal for spin-qubit manipulation in nanowires using the spin-orbit coupling. We discuss the experimental status and describe in further detail the scheme for single-qubit rotations. We present a derivation of the effective two-qubit coupling which can be extended to higher orders in the Coulomb interaction. The analytic expression for the coupling strength is shown to agree with numerics.
Quantum dynamics of a nano-rod under compression
Physics Letters A, 2013
A nano-rod under compression, which is capacitively coupled to a Cooperpair box, can be modeled in terms of a quartic oscillator linearly interacting with a tunnelling pseudo-spin. We have integrated numerically the quantum dynamics of this system in the partial Wigner representation and calculated the pseudo-spin population difference. Depending on the coupling, we have verified that the quantum tunnelling of the oscillator can lead to a more effective reduction of the Rabi oscillation amplitude of the pseudo-spin. Such findings suggests an experimental set-up that might be able to discriminate between the quantum and the classical motion of a nano-rod.
Aspects on entropy squeezing of a two-level atom in a squeezed vacuum
Chaos Solitons & Fractals, 2003
The entropy squeezing and variance squeezing for the entangled state of a single two-level atom interacting with a single electromagnetic field mode in a squeezed vacuum with a broad bandwidth are studied. The exact results are employed to perform a careful investigation of the influence of the various parameters of the system on the atomic inversion as well as the entropy squeezing and variance squeezing. It is shown that features of the quantum entropy are influenced significantly by the photon number, the two-photon correlation strength, and the squeezed phase.
INFORMATION ENTROPY AND SPIN-SQUEEZING IN ATOMIC THREE-LEVEL SYSTEMS
International Journal of Modern Physics B, 2013
We consider the problem of an atomic three-level system in interaction with a radiation field. The time evolution of the system, in atomic ladder and Λ configurations, is solved exactly assuming a coherent-state as the initial atomic state. We calculate the atomic spin-squeezing, the atomic entropy-squeezing, and their variances. We show that the spin-squeezing and the entropy-squeezing exhibit similar time dependence.