(b) Write out the equations for the time dependence of ρ11, ρ22, ρ12 and ρ21 assuming that a light field interaction V = -μ12Ee iωt + c.c. couples only levels |1> and |2>, and that the excited levels exhibit spontaneous decay. (8 marks) (c) Under steady-state conditions, find the ratio of populations in states |2> and |3>. (3 marks) (d) Find the slowly varying amplitude ̃ ρ 12 of the polarization ρ12 = ̃ ρ 12e iωt . (6 marks) (e) In the limiting case that no decay is possible from intermediate level |3>, what is the ground state population ρ11(∞)? (2 marks) 2. (15 marks total) In a 2-level atom system subjected to a strong field, dressed states are created in the form |D1(n)> = sin θ |1,n> + cos θ |2,n-1> |D2(n)> = cos θ |1,n> sin θ |2,n-1>

The Quantum Theory of Light

It is shown that the ordinary semiclassical theory of the absorption of light by exciton states is not completely satisfactory (in contrast to the case of absorption due to interband transitions). A more complete theory is developed. It is shown that excitons are approximate bosons, and, in interaction with the electromagnetic field, the exciton field plays the role of the classical polarization field. The eigenstates of the system of crystal and radiation field are mixtures of photons and excitons. The ordinary one-quantum optical lifetime of an excitation is infinite. Absorption occurs only when "three-body" processes are introduced. The theory includes "local field" effects, leading to the Lorentz local field correction when it is applicable. A Smakula equation for the oscillator strength in terms of the integrated absorption constant is derived.

a Quantum-Mechanical Theory of the Contribution of Excitons to the Complex Dielectric Constant of Crystals.

Wave propagation and group velocity

We review some basic techniques for laser-induced adiabatic population transfer between discrete quantum states in atoms and molecules.

Laser-induced population transfer by adiabatic passage techniques.

心臓病診療プラクティス 16. 心不全を癒す

We propose a robust scheme to generate multi-photon Fock states in an atom-maser-cavity system using adiabatic passage techniques and topological properties of the dressed eigenenergy surfaces. The mechanism is an exchange of photons from the maser field into the initially empty cavity by bichromatic adiabatic passage. The number of exchanged photons depends on the design of the adiabatic dynamics through and around the conical intersections of dressed eigenenergy surfaces.

Generation of multiphoton Fock states by bichromatic adiabatic passage: Topological analysis

We propose a mechanism for producing N-photon states on demand leaking from a single-mode optical cavity interacting with a single atom and a laser pulse. The number of photons can be chosen because it is determined by the Zeeman substructure of the ground state of the atom and its initial state. The deterministic generation of traveling light of 1 <= n <= 2F photons is achieved, when a circularly polarized laser pulse completely transfers the atomic population between Zeeman sublevels of the ground hyperfine state F through far-detuned Raman scattering, thus producing linearly polarized cavity photons. We describe analytically the evolution of optical field taking into account the spontaneous losses and the cavity damping. We analyze the photon statistics showing that it is close to Poissonian light. We show also that this technique provides a deterministic source of a train of identical multiphoton states with a definite number of photons if a sequence of left-and right-circularly polarized laser pulses is applied. The scheme expands the possibilities for using complex internal states of light to transmit data.

Deterministic production of N-photon states from a single atom-cavity system

https://link.aps.org/pdf/10.1103/PhysRevB.94.199902

Erratum: Adiabatic passage mediated by plasmons: A route towards a decoherence-free quantum plasmonic platform [Phys. Rev. B 93 , 045422 (2016)]

We adopt the beam-splitter model for losses to analyze the performance of a recent compact continuous-variable entanglement distillation protocol [A. Datta et al., Phys. Rev. Lett. 108, 060502 (2012)] implemented using realistic quantum memories. We show that the decoherence undergone by a two-mode squeezed state while stored in a quantum memory can strongly modify the results of the preparatory step of the protocol. We find that the well-known method for locally increasing entanglement, phonon subtraction, may not result in entanglement gain when losses are taken into account. Thus, we investigate the critical number ${m}_{c}$ of phonon subtraction attempts from the matter modes of the quantum memory. If the initial state is not de-Gaussified within ${m}_{c}$ attempts, the protocol should be restarted to obtain any entanglement increase. Moreover, the condition ${m}_{c}g1$ implies an additional constraint on the subtraction beam-splitter interaction transmissivity, viz., it should be about $50%$ for a wide range of protocol parameters. Additionally, we consider the average entanglement rate, which takes into account both the unavoidable probabilistic nature of the protocol and its possible failure as a result of a large number of unsuccessful subtraction attempts. We find that a higher value of the average entanglement can be achieved by increasing the subtraction beam-splitter interaction transmissivity. We conclude that the compact distillation protocol with the practical constraints coming from realistic quantum memories allows a feasible experimental realization within existing technologies.

Compact entanglement distillery using realistic quantum memories

Strategies using shaped laser fields to produce and control efficient field-free alignment are analyzed and compared. It is in particular shown that the strategy recently proposed using a shaped laser field combining an adiabatic ramp with a kick is superior to the bipulse strategy.

Stéphane Guérin

Papers

Generation of multiphoton Fock states by bichromatic adiabatic passage: Topological analysis

Deterministic production of N-photon states from a single atom-cavity system

Erratum: Adiabatic passage mediated by plasmons: A route towards a decoherence-free quantum plasmonic platform [Phys. Rev. B 93 , 045422 (2016)]

Compact entanglement distillery using realistic quantum memories

Strategies for efficient field-free molecular alignment and its control