Abstract
Photon subtraction is useful to produce nonclassical states of light addressed to applications in photonic quantum technologies. After a very accelerated development, this technique makes possible obtaining either single photons or optical cats on demand. However, it lacks theoretical formulation enabling precise predictions for the produced fields. Based on the representation generated by the two-mode SU(2) coherent states, we introduce a model of entangled light beams leading to the subtraction of photons in one of the modes, conditioned to the detection of any photon in the other mode. We show that photon subtraction does not produce nonclassical fields from classical fields. It is also derived a compact expression for the output field from which the calculation of conditional probabilities is straightforward for any input state. Examples include the analysis of squeezed-vacuum and odd-squeezed states. We also show that injecting optical cats into a beam splitter gives rise to entangled states in the Bell representation.
Highlights
Nonclassical states of light are very useful to develop photonic quantum technologies [1]
We study the result of injecting optical cat states into the beam splitter, which leads to entangled states in the form of the Bell-basis elements
We have studied how a two-mode entangled light beam can be produced by injecting superpositions of photon-number states into a lossless symmetric beam splitter
Summary
Nonclassical states of light are very useful to develop photonic quantum technologies [1]. Optical cat states can be experimentally prepared by photon subtraction from a squeezed vacuum state [15,16,17,18,19,20,21] and find immediate applications in diverse photonic quantum technologies, including quantum information [22] and quantum teleportation [23]. The entanglement properties of the output fields are strengthened if the input modes contain different number of photons [48] The latter is usually considered by injecting a superposition of photon-number states into one of the input channels and vacuum in the other one [25]. We discuss about the conditions for photon subtraction and derive a compact expression for the two-mode entangled fields produced by a beam splitter. A short appendix includes calculations that are useful to reproduce the results of the main text
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