A photon number density operator in the covariant formulation of quantum electrodynamics

1999 ◽  
Vol 77 (3) ◽  
pp. 167-175
Author(s):  
T Melde
Keyword(s):  
Hilbert Space ◽  
Quantum Electrodynamics ◽  
Density Operator ◽  
Free Field ◽  
Photon Number ◽  
Covariant Formulation ◽  
Number Density ◽  
Number Operator ◽  
New Model ◽  
Fixed Charges

We introduce a new photon number density operator in the Gupta-Bleuler quantized photon field and show that the corresponding total number operator counts transverse photons in the new model. It is also shown that the suggested operator interpreted in the usual Hilbert space counts, in addition, a number of gauge photons for the free field. In the case of two fixed charges it also counts an extra number of scalar photons due the charges.PACS Nos.: 12.20.-m, 14.70.Pw, 42.50.Ar

A quantization of the electromagnetic field

1983 ◽  
Vol 61 (8) ◽  
pp. 1172-1183
Author(s):  
Anton Z. Capri ◽  
Gebhard Grübl ◽  
Randy Kobes
Keyword(s):  
Hilbert Space ◽  
Electromagnetic Field ◽  
Gauge Invariance ◽  
Free Field ◽  
External Source ◽  
Field Level ◽  
Manifest Covariance ◽  
The One ◽  
Physical Spaces

Quantization of the electromagnetic field in a class of covariant gauges is performed on a positive metric Hilbert space. Although losing manifest covariance, we find at the free field level the existence of two physical spaces where Poincaré transformations are implemented unitarily. This gives rise to two different physical interpretations of the theory. Unitarity of the S operator for an interaction with an external source then forces one to postulate that a restricted gauge invariance must hold. This singles out one interpretation, the one where two transverse photons are physical.

Generation of photon number states by cavity quantum electrodynamics

2003 ◽  
pp. 263-275
Author(s):  
S. Brattke ◽  
G. R. Guthöhrlein ◽  
M. Keller ◽  
W. Lange ◽  
B. Varcoe ◽  
...  
Keyword(s):  
Quantum Electrodynamics ◽  
Photon Number ◽  
Cavity Quantum Electrodynamics

FIELD PURIFICATION OF A GENERAL THREE-LEVEL SYSTEM INTERACTING WITH RADIATION

2003 ◽  
Vol 17 (07) ◽  
pp. 253-262 ◽  
Author(s):  
MAHMOUD ABDEL-ATY
Keyword(s):  
Exact Solution ◽  
Electromagnetic Field ◽  
Density Operator ◽  
Photon Number ◽  
Entangled State ◽  
Level System ◽  
Level Atom ◽  
Coherent Field ◽  
Field Purity ◽  
Intensity Dependent Coupling

In this essay we introduce a new Hamiltonian which represents the interaction between a three-level atom and a single electromagnetic field including arbitrary forms of nonlinearities of both the field and the intensity-dependent coupling. We derive an exact solution for the density operator of the system by means of which we study the field purity for the entangled state of the system. Also, the influences of the nonlinearities on the field purity and mean photon number are examined. Under the condition of an initial coherent field, the field purity shows the collapse-revival phenomenon. It is found that features of these phenomenon are sensitive to the changes of different kinds of the nonlinearities.

Signal characters and non-classical properties of quadratically amplified squeezed vacuum

2020 ◽  
pp. 2150028
Author(s):  
Qiang Ke ◽  
Yi-Fan Wang ◽  
Yan-Bei Cheng ◽  
Xue-Xiang Xu
Keyword(s):  
Wigner Function ◽  
Photon Number ◽  
Quadratic Function ◽  
Interaction Parameters ◽  
Intensity Noise ◽  
Number Operator ◽  
Squeezing Effect ◽  
Squeezed Vacuum ◽  
Antibunching Effect ◽  
Noise Squeezing

Based on the squeezed vacuum (SV) and the quadratic function of the photon number operator, we introduce the quadratically amplified squeezed vacuum (QASV) in this paper. We study the intensity, noise, squeezing effect, antibunching effect, and Wigner function of the QASVs. Compared with the SV, the QASVs have distinctive signal characters and possess peculiar non-classical properties in the proper range of interaction parameters.

Total State Dynamics in the GKSL Regime

2017 ◽  
Vol 24 (04) ◽  
pp. 1740014
Author(s):  
Nina Megier ◽  
Walter T. Strunz
Keyword(s):  
Hilbert Space ◽  
Master Equation ◽  
Open System ◽  
Density Operator ◽  
Weak Coupling ◽  
Open Quantum System ◽  
Markov Approximation ◽  
Wigner Representation ◽  
Total State ◽  
Reduced Density

We develop a framework that allows us to describe the dynamics of the total state of an open quantum system and its bosonic environment in the usual Born (weak coupling) and Markov approximation. By shifting the whole time-dependence into an unnormalized s-operator of the open system, the full dynamics is captured by an s-master equation of similar structure than the well-known Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) master equation for the reduced dynamics. By varying the ordering parameter s (0 ≤ s ≤ 1) we obtain the partial Husimi representation (s = 0) and the partial Glauber-Sudarshan representation (s = 1) for the dynamics of the total state. For the reduced density operator the GKSL master equation can be derived easily. The case of s = 1/2, leading to a partial Wigner representation, is helpful to study the overlap of states in the total Hilbert space of system and environment.

CAVITY QUANTUM ELECTRODYNAMICS OF COMPETING ONE AND TWO PHOTON PROCESSES

1996 ◽  
Vol 10 (09) ◽  
pp. 385-391
Author(s):  
AMITABH JOSHI
Keyword(s):  
Electromagnetic Field ◽  
Quantum Electrodynamics ◽  
Dynamical Evolution ◽  
Single Mode ◽  
Cavity Quantum Electrodynamics ◽  
Rabi Splitting ◽  
New Model ◽  
Two Photon ◽  
Photon Transition ◽  
Vacuum Rabi Splitting

We consider a new model of cavity quantum electrodynamics consisting of the interaction of a single mode of electromagnetic field with two non-identical two-level atoms undergoing one and two photon transition respectively in an ideal cavity. The exact analytic results for the vacuum Rabi splitting and the dynamical evolution of the model are given.

scholarly journals Symmetries, Conserved Properties, Tensor Representations, and Irreducible Forms in Molecular Quantum Electrodynamics

Symmetry ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 298 ◽  
Author(s):  
David Andrews
Keyword(s):  
Electromagnetic Field ◽  
Angular Momentum ◽  
Quantum Electrodynamics ◽  
Covariant Formulation ◽  
Continuity Equations ◽  
Symmetry Principles ◽  
Tensor Representations ◽  
Linear And Nonlinear ◽  
Fundamental Transformation ◽  
Robust Framework

In the wide realm of applications of quantum electrodynamics, a non-covariant formulation of theory is particularly well suited to describing the interactions of light with molecular matter. The robust framework upon which this formulation is built, fully accounting for the intrinsically quantum nature of both light and the molecular states, enables powerful symmetry principles to be applied. With their origins in the fundamental transformation properties of the electromagnetic field, the application of these principles can readily resolve issues concerning the validity of mechanisms, as well as facilitate the identification of conditions for widely ranging forms of linear and nonlinear optics. Considerations of temporal, structural, and tensorial symmetry offer significant additional advantages in correctly registering chiral forms of interaction. More generally, the implementation of symmetry principles can considerably simplify analysis by reducing the number of independent quantities necessary to relate to experimental results to a minimum. In this account, a variety of such principles are drawn out with reference to applications, including recent advances. Connections are established with parity, duality, angular momentum, continuity equations, conservation laws, chirality, and spectroscopic selection rules. Particular attention is paid to the optical interactions of molecules as they are commonly studied, in fluids and randomly organised media.

Evolution of the number state in laser process

2015 ◽  
Vol 29 (19) ◽  
pp. 1550139
Author(s):  
Fuyi You ◽  
Junhua Chen ◽  
Hongyi Fan ◽  
Wenhui Jiang
Keyword(s):  
Wigner Function ◽  
Density Operator ◽  
Jacobi Polynomials ◽  
Photon Number ◽  
Laser Process ◽  
Number State ◽  
Degree Of Coherence ◽  
The Mean ◽  
Analytic Expression ◽  
Second Degree

We investigate systematically the evolution of the number state in a laser process by deriving the analytic expression of the density operator and putting it into a normal ordered form. The eigenvalue of the density operator is related to Jacobi polynomials. Then we derive the expression for the mean photon number, the second degree of coherence, the entropy, Wigner function and the photoncount distribution. The nonclassicality is discussed by virtue of the negativity of Wigner function. It is found that the Wigner function is always negative for t < t0, which is independent on the parameter m. On the other hand, the condition for the second degree of coherence larger than 1 is dependent on the parameter m.

Photon number density operatoriE^⋅A^

1995 ◽  
Vol 51 (5) ◽  
pp. 4186-4190 ◽  
Author(s):  
M. Hawton ◽  
T. Melde
Keyword(s):  
Photon Number ◽  
Number Density
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