scholarly journals Homodyne measurement of average photon number

2006 ◽  
Author(s):  
J. G. Webb ◽  
T. C. Ralph ◽  
E. H. Huntington
Keyword(s):  
Photon Number ◽  
Average Photon Number

DYNAMIC PROPERTIES OF THE LARGE-DETUNING CAVITY QED SYSTEM IN THE PRESENCE OF CAVITY DECAY

2008 ◽  
Vol 22 (26) ◽  
pp. 2561-2570
Author(s):  
CHENG-YUAN GAO ◽  
LEI MA ◽  
JIN-MING LIU
Keyword(s):  
Cavity Qed ◽  
Dynamic Properties ◽  
Photon Number ◽  
Quantum Phase Gate ◽  
Cavity Decay ◽  
Phase Gate ◽  
Physical Quantities ◽  
Population Probability ◽  
Average Photon Number ◽  
Epr State

We consider a physical process of two Λ-type three-level atoms interacting with a bimodal cavity including the influence of the cavity decay. We analyze the influence of cavity decay on several physical quantities of the process, such as atomic population probability, residual entanglement, concurrence of two atoms, average population inversion, average photon number, the fidelity for quantum phase gate, and the fidelity of generating atomic EPR state. It is found that all of these physical quantities decrease with the increase of cavity decay when the other relevant parameters are fixed.

NONCLASSICALITY AND DECOHERENCE OF PHOTON-ADDED THERMAL STATE

2010 ◽  
Vol 08 (08) ◽  
pp. 1373-1387 ◽  
Author(s):  
SHU-JING WANG ◽  
XUE-XIANG XU ◽  
SHAN-JUN MA
Keyword(s):  
Thermal State ◽  
Thermal Environment ◽  
Hermite Polynomials ◽  
Photon Number ◽  
Single Variable ◽  
State Characteristic ◽  
Number Formula ◽  
Analytical Expressions ◽  
Average Photon Number ◽  
Photon Number Distribution

Using the normally ordered form of thermal state characteristic of average photon number nc, we introduce the photon-added thermal state (PATS) and investigate its statistical properties, such as Mandel's Q-parameter, photon number distribution (PND), and Wigner function (WF). We then study its decoherence in a thermal environment with average thermal photon number [Formula: see text] and dissipative coefficient κ by deriving analytical expressions of the WF. The nonclassicality is discussed in terms of the negativity of the WF. It is found that the WF is always positive when [Formula: see text] for any number PATS. The expression for time evolution of the PND and the tomogram of PATS are also derived analytically, which are related to hypergeometric function and single variable Hermite polynomials.

scholarly journals Homodyne measurement of the average photon number

2006 ◽  
Vol 73 (3) ◽  
Author(s):  
J. G. Webb ◽  
T. C. Ralph ◽  
E. H. Huntington
Keyword(s):  
Photon Number ◽  
Average Photon Number

AMPLITUDE-SQUARED SQUEEZING IN THE m-PHOTON JAYNES-CUMMINGS MODEL WITH SQUEEZED FIELD INPUT

1992 ◽  
Vol 06 (13) ◽  
pp. 2409-2422 ◽  
Author(s):  
MUBEEN A. MIR ◽  
M.S.K. RAZMI
Keyword(s):  
Ground State ◽  
Photon Number ◽  
Vacuum State ◽  
Squeezed States ◽  
Initial Field ◽  
Squeezed Vacuum State ◽  
Squeezed Vacuum ◽  
Number Formula ◽  
Average Photon Number ◽  
Intensity Dependent Coupling

Amplitude-squared (AS) squeezing has been investigated for the m-photon Jaynes-Cummings model assuming the field to be initially in the squeezed states. The role played by intensity-dependent coupling has also been discussed. It has been shown that for the large initial average photon number [Formula: see text] with odd values of m, AS squeezing revokes permanently whereas with even values it recurs periodically. As m increases the revocation is hastened and the duration of occurrence decreases. Higher values of m for the initial field in a squeezed vacuum state can make one of the quadrature permanently squeezed. The AS squeezing behavior for two initial states of the atom, i.e., ground state versus excited state is also compared.

scholarly journals Macroscopic displaced thermal field as the entanglement catalyst

2007 ◽  
Vol 7 (8) ◽  
pp. 775-781
Author(s):  
S.-B. Zheng
Keyword(s):  
Thermal Field ◽  
Cavity Mode ◽  
Thermal State ◽  
Atomic System ◽  
Photon Number ◽  
Resonant Interaction ◽  
Entangled State ◽  
Cavity Field ◽  
Average Photon Number

We show that entanglement of multiple atoms can arise via resonant interaction with a displaced thermal field with a macroscopic photon-number. The cavity field acts as the catalyst, which is disentangled with the atomic system after the operation. Remarkably, the entanglement speed does not decrease as the average photon-number of the mixed thermal state increases. The atoms may evolve to a highly entangled state even when the photon-number of the cavity mode approaches infinity.

Coherent States and Fock States at Very High Average Photon Numbers

1981 ◽  
Vol 34 (4) ◽  
pp. 357
Author(s):  
GJ Troup ◽  
HS Perlman
Keyword(s):  
Coherent State ◽  
Field Intensity ◽  
Laser Field ◽  
Coherent States ◽  
Photon Number ◽  
Constant Field ◽  
Fock States ◽  
Fock State ◽  
Very High ◽  
Average Photon Number

A laser field may be idealized as a coherent state, but it is often more convenient to use Fock states fQr quantum electrodynamical calculations. A Fock state implies fluctuations in the field intensity, aptl a constant field intensity (coherent state) implies fluctuations in the photon number. Both these effects are discussed rigorously. When the average photon number tends to infinity, these different states become asymptotically indistinguishable.

STUDY ON QUANTUM CORRELATIONS FOR CIRCUIT QED STATES

2013 ◽  
Vol 27 (13) ◽  
pp. 1350056 ◽  
Author(s):  
Y. H. JI ◽  
Y. M. LIU
Keyword(s):  
Quantum Discord ◽  
Relative Phase ◽  
Photon Number ◽  
Quantum Correlations ◽  
Superconducting Qubits ◽  
Squeezed State ◽  
Cavity Field ◽  
Circuit Qed ◽  
Study Results ◽  
Average Photon Number

We investigate the dynamic evolution behaviors of entanglement and geometric quantum discord of coupled superconducting qubits in circuit QED system. We carefully analyze the effect of cavity field quantum state on the quantum entanglement and quantum correlations dynamic behaviors of coupling superconducting qubits. The results show that when the cavity field is in coherent state, with the average photon number increasing, the quantum discord death (including entanglement death) would become more difficult to appear, that is to say prolonging the survival time of quantum correlations will be a benefit for keeping the quantum correlations. When the cavity field is in squeezed state, the squeezed amplitude parameters are all too big or too small to keep the system quantum correlations. However, the further study results show that with the initial relative phase of coupling superconducting increasing, qubits can also keep the quantum correlations.

SECOND-ORDER AND AMPLITUDE-SQUARED SQUEEZING OF THE TWO TWO-LEVEL ATOMS WITH SUPERPOSITION STATE PREPARATION

1993 ◽  
Vol 07 (26) ◽  
pp. 4439-4450 ◽  
Author(s):  
MUBEEN A. MIR
Keyword(s):  
Photon Number ◽  
Vacuum State ◽  
Second Order ◽  
Squeezed State ◽  
Superposition State ◽  
Initial Field ◽  
Squeezed Vacuum State ◽  
Coherent Field ◽  
Number Formula ◽  
Average Photon Number

An analysis of the second-order and amplitude-squared (AS) squeezing is presented for the two atoms prepared in a two-atom squeezed state using coherent and squeezed field inputs. The system produce strong sqeezing and superposition angle (θ) is more effective for small values of average photon number [Formula: see text] as compared to that of large one. The degree of squeezing of both types increases as θ increases for coherent field input with small [Formula: see text]. Some values of θ for the initial field in a squeezed-vacuum state with any value of input squeezing can make one of the quadrature of the both types of squeezing permanently squeezed for T≥0. For the initial field in a more general squeezed state, the second-order and AS squeezing behave randomly for different values of θ.

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