Preparing pure photon number states of the radiation field

Abstract

The quantum mechanical description of a radiation field is based on states that are characterized by the number of photons in a particular mode; the most basic quantum states are those with fixed photon number, usually referred to as number (or Fock) states. Although Fock states of vibrational motion can be observed readily in ion traps, number states of the radiation field are very fragile and difficult to produce and maintain. Single photons in multi-mode fields have been generated using the technique of photon pairs. But in order to generate these states in a cavity, the mode in question must have minimal losses; moreover, additional sources of photon number fluctuations, such as the thermal field, must be eliminated. Here we observe the build-up of number states in a high-Q cavity, by investigating the interaction dynamics of a probe atom with the field. We employ a dynamical method of number state preparation that involves state reduction of highly excited atoms in a cavity, with a photon lifetime as high as 0.2 seconds. (This set-up is usually known as the one-atom maser or 'micromaser'.) Pure states containing up to two photons are measured unambiguously.

Dynamics of coupled qubits interacting with an off-resonant cavity

“…For CdSe, ǫ = 9 and | S|x|X | ∼ 1 nm, such that J ⊥ ≃ 35 meV/(a 2 [nm]) 3 . For small nanocrystals, where, e.g., a 2 ≃ 4 nm, the Förster matrix element is of order J ⊥ ≃ 0.5 meV.…”

“…1,2,3 In addition to the fundamental interest in states formed by superpositions of matter and photon degrees of freedom, the development of cavity-QED has been triggered by possible applications in quantum information schemes. Strong coupling of a qubit and a cavity mode allows one to convert localized qubits into flying qubits suitable for transmission of quantum information.…”

Laser theory in manifest Lindblad form

“…The setup has become known as the 'micromaser' because of its experimental realization with a high-quality cavity [7,8,9]. One line of research has focused on the so-called 'strong coupling regime' that permits the laser mode to be driven into non-classical states [10,11].…”

Generation of decoherence-free displaced squeezed states of radiation fields and a squeezed reservoir for atoms in cavity QED

“…However, in our proposal, as the transition |g ↔ |e is dipole forbidden, these levels can be chosen in a way that the decay rate γ can be very weak, so that Γ eng ≫ γ, making it possible to neglect the term L at ρ at in Eq. (10). Therefore, with the present scheme we have achieved the interaction of an ideal squeezed reservoir and a two-level atomic system.…”

“…On the other hand, the implementation of quantum logic gates in trapped ions [6] or in cavity quantum electrodynamics (QED) [7] and atomic teleportation [8] have contributed to the rapid development of the quantum information area [1]. Through the precise manipulation of the atom-field interaction, many quantum states of light such as the Schrödinger cat states [9] and Fock states [10] have been generated in cavity QED. However, some non-classical states, such as the squeezed states [11] and the two-mode squeezed state [12], have not been attained experimentally so far, either in the microwave or in the optical regimes in cavity QED, through the interaction of atoms and cavity modes.…”