Ghost imaging with engineered quantum states by Hong–Ou–Mandel interference

Abstract

Traditional ghost imaging experiments exploit position correlations between correlated states of light. These correlations occur directly in spontaneous parametric down-conversion, and in such a scenario, the two-photon state usually used for ghost imaging is symmetric. Here we perform ghost imaging using an anti-symmetric state, engineering the two-photon state symmetry by means of Hong-Ou-Mandel interference. We use both symmetric and anti-symmetric states and show that the ghost imaging setup configuration results in object-image rotations depending on the state selected. Further, the object and imaging arms employ spatial light modulators for the all-digital control of the projections, being able to dynamically change the measuring technique and the spatial properties of the states under study. Finally, we provide a detailed theory that explains the reported observations.

Optimal Pump Shaping for Entanglement Control in Any Countable Basis

“…To see this, the downconverted state which is created in the crystal plane is known to be symmetric, and a quantum state's symmetry is an intrinsic property which cannot be altered by a simple change of basis. [ 16 ] To be able to create an anti‐symmetric state using pump shaping and downconversion alone, one would first need to optimize the pump for a particular symmetric but distinguishable bi‐photon state, say , as anti‐symmetric states must consist of distinguishable photons. Thereafter, a hypothetical “downconversion” process occurring inside the nonlinear crystal would need to deterministically create the relative π phase between the eigenstates which compose , depending on the OAM label of the individual photons.…”

“…This, is essence, would entail the crystal acting in a fashion akin to a control gate from quantum computing, [ 47 ] which it most certainly does not (if a nonlinear crystal existed which did display such “control” behavior, one could use it, along with single qubit operations, to create a quantum computer). It is, however, still possible to relatively easily produce an anti‐symmetric Bell state with a few more optical components after the crystal (such as employing Hong–Ou–Mandel filters and Dove prisms [ 16,18 ] ), or via more intricate setups. [ 48 ] Such techniques, however, would be basis‐specific.…”

“…The entangled state can also be altered by physical processes such as quantum interference at a beam splitter, but this allows only particular properties of the states to be crafted, for example, state symmetry. [ 16–18 ] Since the bi‐photon state is given by the overlap integral of the pump light's transverse mode and that of the two entangled photons, there are two obvious routes to manipulating the resulting modal spectrum. The first is to use post‐selection, whereby one alters in which basis one measures and changes the efficiency of each measurement, for example, to flatten the modal spectrum [ 19 ] and concentrate entanglement.…”

Entangled light–matter interactions and spectroscopy

“…For example, quantum ghost imaging relies on the coherence between the down-converted beams to record the image of an object with photons that do not interact with it directly. 59,[66][67][68][69][70][71][72] Quantum optical coherence tomography (QOCT) offers improved resolution and sensitivity by exploiting the dispersion cancelling properties of the entangled wavepacket, as well as the anticorrelation between entangled pairs, to construct quantum interference patterns corresponding to sample depth. [73][74][75] Entangled photons can also increase measurement sensitivities as compared with classical photons.…”

Improvement of phase sensitivity in SU(1,1) interferometer via a Kerr nonlinear

“…Quantum metrology has a close relation to variousimportant information areas, such as Bose-Einstein condensate [1][2][3], gravitational wave detection [4,5], and quantum imaging [6][7][8]. It has been widely concerned and highly developed in recent years.…”