Within the framework of thermofield dynamics, the wavefunctions of the thermalized displaced number and squeezed number states are given in the coordinate representation. Furthermore, the time evolution of these wavefunctions is considered by introducing a thermal coordinate representation, and we also calculate the corresponding probability densities, average values and variances of position coordinate, which are consistent with results in the literature.
The quantum Rabi model accepts analytical solutions in the so-called degenerate qubit and relativistic regimes with discrete and continuous spectrum, in that order.We show that solutions in the laboratory frame are the superposition of even and odd displaced number states, in the former, and infinitely squeezed coherent states, in the latter, of the boson field correlated to the internal states of the qubit. We propose a single parameter model that interpolates between these discrete and continuous spectrum regimes to study the spectral statistics for first and second neighbor differences befo…
Full-Period Optical Phase Estimation with Heisenberg Scaling Using Displaced Squeezed States and Gaussian Measurements
Institute for Quantum Science and Technology, University of Calgary（卡尔加里大学量子科学与技术研究所）；Center for Quantum Information and Control, Department of Physics and Astronomy, University of New Mexico（新墨西哥大学物理与天文系量子信息与控制中心）；Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México（墨西哥国立自治大学物理科学研究所）
We predict that the phase-dependent error distribution of locally unentangled quantum states directly affects quantum parameter estimation accuracy. Therefore, we employ the displaced squeezed vacuum (DSV) state as a probe state and investigate an interesting question of the phase-sensitive nonclassical properties in DSV's metrology. We found that the accuracy limit of parameter estimation is a function of the phase-sensitive parameter $ϕ-θ/2$ with a period $π$. We show that when $ϕ-θ/2$ $\in \left[ kπ/2,3kπ/4\right) \left( k\in \mathbb{Z}\right)$, we can obtain the accuracy of parameter estim…
Generation of decoherence-free displaced squeezed states of radiation fields and a squeezed reservoir for atoms in cavity QED
我们提出了一种方法来设计一个有效的反Jaynes-Cumming和Jaynes-Cumming原子系统和单腔模式之间的相互作用，并展示了如何在油藏工程过程中使用它。为了构造有效哈密顿量，我们分析了在经典场驱动下，处于λ位形的原子系统与单腔模的相互作用.利用这种相互作用，我们首次给出了如何产生无消相干的腔场位移压缩态。在我们的方案中，原子束作为一个水库的辐射场被困在腔内，最近所采用的S。Pielawa等人[Phys. Rev. Lett. 98，240401（2007）]以在高Q谐振器中产生爱因斯坦-波多尔斯基-罗森纠缠辐射态。在我们的方案中，所有的原子都必须在基态下准备，并且如在引用的文章中那样，既不需要原子检测，也不需要原子与腔模之间的精确相互作用时间。从这种相互作用中，我们也可以为原子系统生成一个理想的压缩库。为此，我们必须假设，除了工程原子-场相互作用之外，腔场的强衰减（即，腔衰减必须比有效的原子-场耦合强得多）。利用这个方案，可以检验压缩库中原子动力学中的一些有趣的效应。
We present an exact analytical solution for a one-dimensional zigzag waveguide array with first and second neighbor interactions. It is found that the waveguide system possess a classical analog to the displaced squeezed number states. The exact solution was compared directly with the numerical solution showing a perfect agreement between both results. The implication of a linear index of refraction changing as a function of the site number is also studied. In this case, we show that the first neighbor interaction strongly influences the periodicity of Bloch oscillations.
The dynamical behavior of quantum coherence of a displaced squeezed thermal state in contact with an external bath is discussed in the present work. We use a Fano-Anderson type of Hamiltonian to model the environment and solve the quantum Langevin equation. From the solution of the quantum Langevin equation we obtain the Green's functions which are used to calculate the expectation value of the quadrature operators which are in turn used to construct the covariance matrix. We use a relative entropy based measure to calculate the quantum coherence of the mode. The single mode squeezed thermal s…
A novel, unexplored nonperturbative deep-strong coupling (npDSC) achieved in superconducting circuits has been studied in the anisotropic Rabi model by the generalized squeezing rotating-wave approximation (GSRWA). Energy levels are evaluated analytically from the reformulated Hamiltonian and agree well with numerical ones under a wide range of coupling strength. Such improvement ascribes to deformation effects in the displaced-squeezed state presented by the squeezed momentum variance, which are omitted in the previous displaced state. The population dynamics confirm the validity of our appro…
Near-optimal discrimination of displaced squeezed binary signals using displacement, inverse-squeezing, and photon-number-resolving detection
Information Support Force Engineering University（信息支援部队工程大学）；Guangxi Key Laboratory of Multimedia Communications and Network Technology, Guangxi University（广西大学）；Henan Key Laboratory of Quantum Information and Cryptography, SSF IEU（河南量子信息与密码学重点实验室）；Wuhan Maritime Communication Research Institute（武汉海事通信研究所）
It is shown that the time evolution of the squeezed and displaced state may be obtained by solving the Heisenberg equation of motion of an appropriate operator and finding the eigenstates of the time evolved operator. The connection between symplectic transformations and squeezing is explored.
A method is introduced which allows to measure normal-ordered moments of the displaced photon-number operator up to high orders. It is based on unbalanced homodyne correlation measurements, the local oscillator being replaced by a displaced dephased laser. The measured moments yield a simple approximation of the full quantum state, which is obtained without the need of photon-number resolution. Quantum properties of light are efficiently certified through the direct detection of normal-ordered observables, which is illustrated for a weakly squeezed vacuum and a single-photon-added thermal stat…
We introduce transformation matrix connecting sets of the displaced states with different displacement amplitudes. Arbitrary pure one-mode state can be represented in new basis of the displaced number (Fock) states ( representation) by multiplying the transposed transformation matrix on a column vector of initial state. Analytical expressions of the representation of superposition of vacuum and single photon and two-mode squeezed vacuum (TMSV) are obtained. On the basis of the developed mathematical formalism, we consider the mechanism of interaction between qubits which is based on their disp…
Optimizing photon-number distributions of Gaussian states in the presence of loss: Towards minimizing the impact of loss in Gaussian boson sampling
Friedrich-Schiller-University Jena（耶拿弗里德里希·席勒大学）；Institute of Condensed Matter Theory and Optics, Friedrich-Schiller-University Jena（耶拿弗里德里希·席勒大学凝聚态理论与光学研究所）；Fraunhofer Institute for Applied Optics and Precision Engineering IOF（弗劳恩霍夫应用光学和精密工程研究所）
It is shown that the maximal phase sensitivity of a two-path interferometer with high-intensity coherent light and squeezed vacuum in the input ports can be achieved by photon-number-resolving detection of only a small number of photons in a dark output port. It is then possible to achieve the quantum Cramér-Rao bound of the two-path interferometer using only the field displacement dependence of the photon number statistics in the single mode output of the dark port represented by a field-displaced squeezed vacuum state. We find that, at small field displacements, it is not sufficient to use t…
