Abstract
We investigate coherent perfect absorption (CPA) in quantum optics, in particular when pairs of squeezed coherent states of light are superposed on an absorbing beam splitter. First, by employing quantum optical input-output relations, we derive the absorption coefficients for quantum coherence and for intensity, and reveal how these will differ for squeezed states. Secondly, we present the remarkable properties of a CPA-gate: two identical but otherwise arbitrary incoming squeezed coherent states can be completely stripped off their coherence, producing a pure entangled squeezed vacuum state that with its finite intensity escapes from an otherwise perfect absorber. Importantly, this output state of light is not entangled with the absorbing beam splitter by which it was produced. Its loss-enabled functionality makes the CPA gate an interesting new tool for continuous-variable quantum state preparation.
Highlights
Coherent perfect absorption (CPA) of light [1] is an interferenceassisted absorption process that in its simplest form can take place when two coherent beams impinge on the opposite sides of an absorbing beam splitter
We investigated the coherent absorption of light when two squeezed coherent beams are superposed on an absorbing beam splitter
We first reconsidered the generic case of two incoming bare coherent states and distinguished two types of absorption, namely, of quantum coherence introduced to the system by the complex amplitude α and of intensity
Summary
Coherent perfect absorption (CPA) of light [1] is an interferenceassisted absorption process that in its simplest form can take place when two coherent beams impinge on the opposite sides of an absorbing beam splitter. Squeezed vacuum was proposed to engineer interactions between electric dipoles [41] In this contribution, we distinguish between the usual absorption of intensity and that of quantum coherence, the latter measured as the coherent degree of freedom in Glauber’s sense [42]. The requirement for perfect absorption of coherence becomes the complete indistinguishability of the incoming fields This requirement holds for squeezed coherent states of light as input.
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