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- 摘要
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Harvesting correlations from thermal and squeezed coherent states
摘要： We study the harvesting of entanglement and mutual information by Unruh-DeWitt particle detectors from thermal and squeezed coherent field states. We prove (for arbitrary spatial dimensions, switching profiles and detector smearings) that while the entanglement harvesting ability of detectors decreases monotonically with the field temperature T, harvested mutual information grows linearly with T. We also show that entanglement harvesting from a general squeezed coherent state is independent of the coherent amplitude, but depends strongly on the squeezing amplitude. Moreover, we find that highly squeezed states (i) allow for detectors to harvest much more entanglement than from the vacuum, and (ii) ensure that the entanglement harvested does not decay with their spatial separation. Finally, we analyze the spatial inhomogeneity of squeezed states and its influence on harvesting, and investigate how much entanglement one can actually extract from squeezed states when the squeezing is bandlimited.
关键词： Unruh-DeWitt detectors,thermal states,entanglement harvesting,quantum field theory,squeezed coherent states,mutual information
更新于2025-09-23 15:22:29
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Direct characterization of linear and quadratically nonlinear optical systems
摘要： A central task in quantum-information processing is to characterize quantum processes. In the realm of optical quantum-information processing, this amounts to characterizing the transformations of the mode creation and annihilation operators. This transformation is unitary for linear optical systems, whereas these yield the well-known Bogoliubov transformations for systems with Hamiltonians that are quadratic in the mode operators. In this paper, we propose a shot-noise limited scheme for characterizing both these kinds of evolutions by employing a modified Mach-Zehnder interferometer. In order to characterize a N -mode device, we require O(N 2) measurements. Although it suffices to use coherent states for the characterization of linear optical systems, we additionally require single photons to characterize quadratically nonlinear optical systems.
关键词： Bogoliubov transformations,Mach-Zehnder interferometer,optical systems,quantum-information processing,coherent states,single photons
更新于2025-09-23 15:21:21
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Bi-squeezed states arising from pseudo-bosons
摘要： Extending our previous analysis on bi-coherent states, we introduce here a new class of quantum mechanical vectors, the bi-squeezed states, and we deduce their main mathematical properties. We relate bi-squeezed states to the so-called regular and non regular pseudo-bosons. We show that these two cases are different, from a mathematical point of view. Some physical examples are considered.
关键词： squeezed states,pseudo-bosons,coherent states
更新于2025-09-23 15:19:57
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Quantum Dual Signature with Coherent States Based on Chained Phase-Controlled Operations
摘要： A novel encryption algorithm called the chained phase-controlled operation (CPCO) is presented in this paper, inspired by CNOT operation, which indicates a stronger correlation among message states and each message state depending on not only its corresponding key but also other message states and their associated keys. Thus, it can prevent forgery effectively. According to the encryption algorithm CPCO and the classical dual signature protocols, a quantum dual signature scheme based on coherent states is proposed in this paper. It involves three participants, the customer Alice, the merchant Bob and the bank Trent. Alice expects to send her order message and payment message to Bob and Trent, respectively. It is required that the two messages must be linked to guarantee the payment is paid for the corresponding order. Thus, Alice can generate a quantum dual signature to achieve the goal. In detail, Alice firstly signs her two messages with the shared secret key. Then She connects the two signatures into a quantum dual signature. Finally, Bob and Trent severally verify the signatures of the order message and the payment message. Security analysis shows that our scheme can ensure its security against forgery, repudiation and denial. In addition, simulation experiments based on the Strawberry Fields platform are performed to valid the feasibility of CPCO. Experimental results demonstrate that CPCO is viable and the expected coherent states can be acquired with high fidelity, which indicates that the encryption algorithm of the scheme can be implemented on quantum devices effectively.
关键词： the chained phase-controlled operations,coherent states,e-payment system,quantum dual signature
更新于2025-09-23 15:19:57
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Photon-added entangled Baruta??Girardello coherent states: non-classicality and generation
摘要： In continuation of previous papers where the addition of photons into the two-mode entangled quantum states was studied, we proposed a scheme to establish and generate photon-added ‘entangled Barut–Girardello coherent states’ (PAEBGCSs), by applying photon creation operators on the two-mode EBGCSs, where the latter is introduced by Hach et al. (JOSA B 35:2433, 2018), as a new class of quantum states connected to the simple harmonic oscillator and generated through a Mach–Zehnder interferometer, and the dynamics of their entanglement is analyzed in details. In addition, the EBGCSs include strong non-classical properties; then, to gain insight into the effectiveness of photon addition to them and comparing with the case already discussed as the photon-added entangled Klauder–Perelomov coherent states, we present a general analysis of non-classical properties such as photon statistics and squeezing and photon number distribution. We also derive the concurrence measure to quantify the entanglement of these states and look for conditions that provide information on whether these become maximally entangled. We show that the photon addition plays an important role in non-classical effects, and this operation can be applied to enhance the entanglement of the PAEBGCSs. For instance, entanglement preserving against quantum polarization is occurred by adding photons to the EBGCSs. Finally, an experimental procedure for generating the PAEBGCSs in the framework of cavity quantum electrodynamics is established.
关键词： non-classicality,quantum optics,Photon-added entangled Barut–Girardello coherent states,generation,quantum information
更新于2025-09-23 15:19:57
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Polynomial Heisenberg algebras, multiphoton coherent states and geometric phases
摘要： In this paper we will realize the polynomial Heisenberg algebras through the harmonic oscillator. We are going to construct then the Barut-Girardello coherent states, which coincide with the so-called multiphoton coherent states, and we will analyze the corresponding Heisenberg uncertainty relation and Wigner distribution function for some particular cases. We will show that these states are intrinsically quantum and cyclic, with a period being a fraction of the oscillator period. The associated geometric phases will be as well evaluated.
关键词： coherent states,Polynomial Heisenberg algebras,multiphoton coherent states,geometric phases
更新于2025-09-19 17:15:36
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Fluctuations of the hermitian phase operator of electromagnetic field for quantum phase superpositions of coherent states
摘要： Quantum-statistical properties of the phase of electromagnetic field in the case of phase superpositions of coherent states of the type Nα,β,ξ (|α? + e^iξ |β?) have been studied. Formulas for the average values and fluctuations (variances) of Hermitian phase operator ??θ of the electromagnetic field (so-called Pegg–Barnett optical phase operator) in the case of general superposition of coherent states are obtained and analysed. The states of phase superpositions of the 'Schr?dinger cat' type Nα,?α,ξ (|α? + e^iξ |?α?), ?β = ?α + π, and superpositions of coherent states of the type Nα,α?,ξ (|α? + e^iξ |α??), ?β = ??α, are considered separately.
关键词： quantum phase fluctuations,Hermitian phase operator,coherent states superpositions
更新于2025-09-19 17:15:36
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Physical and nonclassical properties of the interaction between a four-level atom and field in coherent state of Morse potential
摘要： The quantum system of the field initially defined by the k-photon-added Morse potential coherent states (MPCSs) of the radiation field interacting with a four-level atom (FLA) was studied. The physical and non-classical properties of the field defined by the MPCS system were quantified using the Mandel parameter. The effect of time-dependent coupling (TDC) on the atomic speed was examined. Moreover, the dynamic properties of the non-local correlation between the FLA and MPCS radiation field were studied and compared with those of the geometric phase. We also investigated the influence of the initial interaction conditions and different system parameters on the evolution of the non-local correlation, Mandel parameter, and geometric phase. The relationships between the geometric phase, Mandel parameter, and non-local correlation with TDC were explored.
关键词： Entanglement,Morse potential coherent states,Mandel parameter,Geometric phase
更新于2025-09-19 17:15:36
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Enhancing entanglement of entangled coherent states via a f-deformed photon-addition operation
摘要： In this paper, we introduce a new kind of photon-added entangled coherent states (PA-ECSs), by performing repeatedly a f -deformed photon-addition (DPA) operation, A? = f (?n)a?, on each mode of the entangled coherent states (ECSs), |Ψ±(α)(cid:3). By choosing a particular deformation function f (?n), we study how the entanglement properties can be enhanced by DPA operation. As a result, we show that both the single and two-mode DPA operation can be used to improve the entanglement of |Ψ+(α)(cid:3), where the e?ects of improvement by two-mode DPA operation are more prominent than those by single-mode DPA operation, in any amplitude regime. Moreover, our results show there exists a family of coherent amplitudes |α| such that the two-mode DPA operation preserves the maximal entanglement of the odd ECSs |Ψ?(α)(cid:3), where the non-deformed photon-addition operation a? suppresses the entanglement amount. Finally, a theoretical scheme for the physical generation of the introduced states based on a Jaynes-Cummings model with intensity-dependent couplings is proposed.
关键词： entangled coherent states,entanglement enhancement,Jaynes-Cummings model,f-deformed,photon-addition
更新于2025-09-12 10:27:22
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Characterizing nonstationary coherent states in globally coupled conformist and contrarian oscillators
摘要： For decades, the description and characterization of nonstationary coherent states in coupled oscillators have not been available. We here consider the Kuramoto model consisting of conformist and contrarian oscillators. In the model, contrarians are chosen from a bimodal Lorentzian frequency distribution and ?ipped into conformists at random. A complete and systematic analytical treatment of the model is provided based on the Ott-Antonsen ansatz. In particular, we predict and analyze not only the stability of all stationary states (such as the incoherent, the π , and the traveling-wave states), but also that of the two nonstationary states: the Bellerophon and the oscillating-π state. The theoretical predictions are fully supported by extensive numerical simulations.
关键词： nonstationary coherent states,Kuramoto model,oscillating-π state,Bellerophon state,Ott-Antonsen ansatz
更新于2025-09-12 10:27:22