scholarly journals SQUEEZED VACUA AND THE QUANTUM STATISTICS OF COSMOLOGICAL PARTICLE CREATION

1994 ◽  
Vol 09 (07) ◽  
pp. 991-1007 ◽  
Author(s):  
B. L. HU ◽  
G. KANG ◽  
A. MATACZ
Keyword(s):  
Coherent State ◽  
Particle Number ◽  
Particle Creation ◽  
Space Time ◽  
Quantum Statistics ◽  
Squeezed States ◽  
Quantum Fields ◽  
Squeezed State ◽  
Initial State ◽  
Systematic Description

We use the language of squeezed states to give a systematic description of two issues in cosmological particle creation: (a) Dependence of particle creation on the initial state specified; we consider in particular the number state, the coherent state and the squeezed state; (b) the relation of spontaneous and stimulated particle creation and their dependence on the initial state. We also present results for the fluctuations in particle number in anticipation of its relevance to defining noise in quantum fields and the vacuum susceptibility of space–time.

QUANTUM EFFECTS OF A PARTICLE IN AN INFINITE SQUARE WELL WITH A MOVING WALL

2000 ◽  
Vol 14 (10) ◽  
pp. 1059-1065 ◽  
Author(s):  
JIAN ZOU ◽  
BIN SHAO
Keyword(s):  
Wave Packet ◽  
Boundary Conditions ◽  
Coherent State ◽  
Dynamical Behavior ◽  
Squeezed State ◽  
Initial State ◽  
One Dimensional ◽  
Moving Wall ◽  
Quantum Behavior ◽  
Square Well

The quantum behavior of a particle in a one-dimensional infinite square well potential with a moving wall is studied. The particle is assumed to be initially prepared in the coherent state (Gaussian wave packet) and although the boundary is far from the particle, it is shown that the changing of the boundary conditions can instantaneously affect the dynamical behavior of the particle. It is also shown that the initial state can evolve into a squeezed state, and in some cases the spreading of the wavepacket could be suppressed. Finally the Pancharatnam phase is also discussed.

scholarly journals Higher order properties and Bell inequality violation for the three-mode enhanced squeezed state

2010 ◽  
Vol 88 (5) ◽  
pp. 349-356
Author(s):  
Shuang-Xi Zhang ◽  
Hong-Chun Yuan ◽  
Hong-Yi Fan
Keyword(s):  
Coherent State ◽  
Bell Inequality ◽  
Higher Order ◽  
Photon Statistics ◽  
Squeezed States ◽  
Squeezed State ◽  
Squeezed Coherent State ◽  
Wigner Representation ◽  
Squeezing Operator

By extending the usual two-mode squeezing operator S2 = exp[iλ(Q1P2 + Q2P1)] to the three-mode squeezing operator S3 = exp{iλ[Q1(P2 + P3) + Q2(P1 + P3) + Q3(P1 + P2)]}, we obtain the corresponding three-mode squeezed coherent state. The higher order properties of this state, such as higher order squeezing and higher order sub-Possonian photon statistics, are investigated. It is found that the new squeezed state not only can be squeezed to all even orders but also exhibits squeezing enhancement compared with the usual cases. In addition, we examine the violation of the Bell inequality for the three-mode squeezed states by using the formalism of Wigner representation.

scholarly journals Space–time-bounded quantum fields for detection processes

2014 ◽  
Vol 470 (2164) ◽  
pp. 20130465
Author(s):  
Fernando J. Aguayo ◽  
George Jaroszkiewicz
Keyword(s):  
Space Time ◽  
The State ◽  
Detector System ◽  
Time Dependent ◽  
Quantum Field ◽  
Quantum Fields ◽  
Initial State ◽  
Field Detection ◽  
Detection Model ◽  
Irreversible Evolution

We discuss a quantum field detection model comprising two types of detection procedures: maximal detection, where the initial state of the system and detectors undergoes an irreversible evolution, and minimal detection, where the system–detector interaction consists of a small, reversible coupling and posterior maximal detection performed over the detector system. Combined, these detection procedures allow for a time-dependent description of signalling experiments involving yes/no type of questions. A particular minimal detection model, stable in the presence of the vacuum, is presented and studied, successfully reproducing the localization of the state after a detection.

OSCILLATORY PHASE OF NONCLASSICAL THERMAL INFLATON IN FRW UNIVERSE

2010 ◽  
Vol 19 (07) ◽  
pp. 1147-1195 ◽  
Author(s):  
K. K. VENKATARATNAM ◽  
P. K. SURESH
Keyword(s):  
Particle Production ◽  
Particle Creation ◽  
Squeezed States ◽  
Semiclassical Theory ◽  
Squeezed State ◽  
Nonclassical States ◽  
Frw Universe ◽  
Semiclassical Gravity ◽  
Oscillatory Phase ◽  
Classical Gravity

A minimally coupled nonclassical homogeneous scalar field is examined in the flat FRW universe in the semiclassical theory of gravity. Particle production in thermal coherent and squeezed states is studied for the flat FRW universe, in the oscillatory phase of the inflaton. Solutions for the semiclassical Friedmann equations are obtained in the thermal nonclassical states. Validity of the semiclassical theory is examined in the thermal coherent and squeezed states in the oscillatory phase of inflaton. Particle creation can be enhanced due to thermal and quantum effects. Quantum fluctuations of the inflaton in thermal coherent and squeezed state formalisms are also studied. Classical gravity differ from semiclassical gravity in the thermal coherent state only by an amplitude factor.

scholarly journals Scattering-lens based quantum imaging beyond shot noise

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dong Li ◽  
Yao Yao
Keyword(s):  
Coherent State ◽  
Shot Noise ◽  
Quantum Noise ◽  
Signal To Noise Ratio ◽  
Optical Diffraction ◽  
Squeezed States ◽  
Squeezed State ◽  
Signal To Noise ◽  
Alternative Scheme ◽  
Noise Ratio

AbstractThe scheme of optical imaging using scattering lens can provide a resolution beyond the classical optical diffraction limit with a coherent-state input. Nevertheless, due to the shot noise of the coherent state, the corresponding signal-to-noise ratio and resolution are both still shot-noise-limited. In order to circumvent this problem, we theoretically propose an alternative scheme where the squeezed state (with a sub-shot noise) is considered as input and the quantum noise is then suppressed below the shot-noise level. Consequently, when comparing with the previous imaging scheme (using combination of coherent state and scattering lens), our proposal is able to achieve an enhanced signal-to-noise ratio for a given scattering lens. Meanwhile, it is demonstrated that the resolution is also improved. We believe that this method may afford a new way of using squeezed states and enable a higher performance than that of using coherent state and scattering lens.

scholarly journals Stimulated emission of relic gravitons and their super-Poissonian statistics

2019 ◽  
Vol 34 (23) ◽  
pp. 1950185 ◽  
Author(s):  
Massimo Giovannini
Keyword(s):  
Coherent State ◽  
Second Order ◽  
Stimulated Emission ◽  
Initial State ◽  
Einstein Distribution ◽  
Hubble Radius ◽  
Initial States ◽  
Bose Einstein ◽  
Final Degree ◽  
Poissonian Statistics

The degree of second-order coherence of the relic gravitons produced from the vacuum is super-Poissonian and larger than in the case of a chaotic source characterized by a Bose–Einstein distribution. If the initial state does not minimize the tensor Hamiltonian and has a dispersion smaller than its averaged multiplicity, the overall statistics is by definition sub-Poissonian. Depending on the nature of the sub-Poissonian initial state, the final degree of second-order coherence of the quanta produced by stimulated emission may diminish (possibly even below the characteristic value of a chaotic source) but it always remains larger than one (i.e. super-Poissonian). When the initial statistics is Poissonian (like in the case of a coherent state or for a mixed state weighted by a Poisson distribution) the degree of second-order coherence of the produced gravitons is still super-Poissonian. Even though the quantum origin of the relic gravitons inside the Hubble radius can be effectively disambiguated by looking at the corresponding Hanbury Brown–Twiss correlations, the final distributions caused by different initial states maintain their super-Poissonian character which cannot be altered.

LEGENDRE POLYNOMIALS AS THE NORMALIZATION OF PHOTON-SUBTRACTED SQUEEZED STATES

2009 ◽  
Vol 24 (20) ◽  
pp. 1597-1603 ◽  
Author(s):  
HONG-YI FAN ◽  
LI-YUN HU ◽  
XUE-XIANG XU
Keyword(s):  
Legendre Polynomial ◽  
Legendre Polynomials ◽  
Hermite Polynomial ◽  
Vacuum State ◽  
Squeezed States ◽  
Squeezed State ◽  
Normalization Factor ◽  
Squeezed Vacuum State ◽  
Squeezed Vacuum ◽  
Excitation State

By converting the photon-subtracted squeezed state (PSSS) to a squeezed Hermite-polynomial excitation state we find that the normalization factor of PSSS is an m-order Legendre polynomial of the squeezing parameter, where m is the number of subtracted photons. Some new relations about the Legendre polynomials are obtained by this analysis. We also show that the PSSS can also be treated as a Hermite-polynomial excitation on squeezed vacuum state.

Berry phase for the SU(1,1) coherent state

1988 ◽  
Vol 66 (11) ◽  
pp. 978-980 ◽  
Author(s):  
Fan Hong-Yi ◽  
H. R. Zaidi
Keyword(s):  
Coherent State ◽  
General Expression ◽  
Berry Phase ◽  
Squeezed States

We derive a general expression for the Berry phase for the case of the SU(1,1) coherent state. The results are also applicable to one- and two-mode squeezed states.

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