Exponentially Enhanced Light-Matter Interaction, Cooperativities, and Steady-State Entanglement Using Parametric Amplification

Abstract

We propose an experimentally feasible method for enhancing the atom-field coupling as well as the ratio between this coupling and dissipation (i.e., cooperativity) in an optical cavity. It exploits optical parametric amplification to exponentially enhance the atom-cavity interaction and, hence, the cooperativity of the system, with the squeezing-induced noise being completely eliminated. Consequently, the atom-cavity system can be driven from the weak-coupling regime to the strong-coupling regime for modest squeezing parameters, and even can achieve an effective cooperativity much larger than 100. Based on this, we further demonstrate the generation of steady-state nearly maximal quantum entanglement. The resulting entanglement infidelity (which quantifies the deviation of the actual state from a maximally entangled state) is exponentially smaller than the lower bound on the infidelities obtained in other dissipative entanglement preparations without applying squeezing. In principle, we can make an arbitrarily small infidelity. Our generic method for enhancing atom-cavity interaction and cooperativities can be implemented in a wide range of physical systems, and it can provide diverse applications for quantum information processing.

Squeezing‐Enhanced Atom–Cavity Interaction in Coupled Cavities with High Dissipation Rates

“…The ratio g r p /g 0 are obtained by comparing the oscillation periods for various r p with the oscillation period for r p = 0. [15,17] and also generalized in our recent study. κ 1 , κ 2 , and γ are the decay rates of the primary cavity a, the auxiliary caivty c and the atom, respectively; N = sinh 2 (r e ) denotes the mean photon number of the squeezed field, and M = cosh(r e ) sinh(r e )e iθe denotes the strength of the two-photon correlation.…”

“…[13,19] For atoms which are highly detuned from the field mode, excitation may transfer between them without populating the field mode. [15,17], we have demonstrated an enhancement of the dipole+dipole interaction between two atoms trapped in an optical cavity. [15,17], we have demonstrated an enhancement of the dipole+dipole interaction between two atoms trapped in an optical cavity.…”

“…The influence of the cavity decay κ 1 on the adiabatic elimination of the squeezed cavity mode a s is discussed in the Appendix. [15] This may be understood clearly from the analytical expression of the effective coupling (see Equation (4)). It is noted that there is a small invalid region of enhancement with g rp /g 0 < 1.…”

“…[15][16][17][18] It is well known that in cavity QED system, the excitation of cavity field can be eliminated completely by confining and coupling two atoms to a single cavity. [15][16][17][18] It is well known that in cavity QED system, the excitation of cavity field can be eliminated completely by confining and coupling two atoms to a single cavity.…”

“…The first primary cavity (with resonance frequency ω a and decay rate κ 1 ) supports optical mode a, while the second auxiliary cavity (with resonance frequency ω c and decay rate κ 2 ) supports optical mode c. Two cavities are coupled by the photon hopping with strength J , which can be tuned by changing the distance between them. [17] A high bandwidth squeezed vacuum field, which can be thought of as a squeezed vacuum reservoir (with squeezing parameter r e and reference phase θ e ), is injected into the primary cavity [15] . Notably, the nonlinearity of the medium is used to induce a squeezed cavity mode.…”