Modified two-photon interference achieved by the manipulation of entanglement

Abstract

In this theoretical study we demonstrate that entangled states are able to significantly extend the functionality of Hong-Ou-Mandel (HOM) interferometers. By generating a coherent superposition of parametric-down-conversion photons and spatial entanglement in the input channel, the coincidence probability measured at the output changes from a typical HOM-type dip (photon bunching) into much richer patterns including an anti-bunching peak and rapid oscillation fringes with twice the optical frequency. The considered system should be realizable on a single chip using current waveguide technology in the LiN bO3 platform. [4][5][6], and quantum algorithms [7,8]. The highly attractive hyperentangled states extend possibilities of quantum technologies, allowing new quantum communication protocols, superdense teleportation [10], and objects with higher dimensionality [9]. Therefore the generation and application of photon states with a high degree of entanglement and hyperentangled states is an intensely studied topic in quantum optics.An important element in a computational infrastructure based on photons are quantum interferometers which allow to measure the degree of indistinguishability of photons. Such interferometers can be realized using the well-known two-photon Hong-Ou-Mandel (HOM) interference, which was demonstrated in several systems [11][12][13][14][15][16][17].For practical large-scale applications in quantum information processing free-space set-ups are not very reliable because of the experimental complexity that is required to achieve and maintain a precise and stable adjustment between the elements and due to the significant size of such systems. However, due to their small size and high stability integrated quantum optical systems [18] are very promising in this direction. Furthermore, they provide an attractive platform for the realization of a wide range of functionalities including quantum simulations [19,20], boson sampling [21-23], quantum computation, and quantum communication processing [24].In this paper, we propose and analyze a device which can be realized on a single integrated platform and is able to manipulate the two-photon coincidence probability by interference and to create hyperentanglement. The photon pair generation is incorporated into the system using an on-chip parametric-down-conversion (PDC) [25][26][27][28] source. We theoretically show that the creation of spatially-entangled photons in a singlet Bell state is possible in such a device and that the entanglement leads to novel features in the coincidence probability. In particular, different regimes of bunching (HOM-type dips) and anti-bunching (singlet Bell state) and rapid interference fringes corresponding to twice the optical frequency are predicted. Simultaneously, frequency correlations are preserved in the system which leads to the creation a hyperentanglement, see Fig. 1. FIG. 1. Two photons generated in a PDC process have frequency correlations. The creation of spatial entanglement between the photons leads to a hy...

Quantum Pyragas control: Selective control of individual photon probabilities

“…30%. Altogether, this demonstrates that a single TLS can be used to efficiently generate a two-photon state with a high degree of control [56,57]. Furthermore, it shows that non-Markovian quantum Pyragas control expands the possibilities to shape, tailor and manipulate individual photon-probabilities.…”

Spatial entanglement and state engineering via four-photon Hong-Ou-Mandel interference

“…In this work we consider a linear quantum interferometer with a polarization roatation [19] in the four-photon regime. The schematic setup is presented in Fig.…”

“…The P 22 probability has a complicated structure with two dips corresponding to the HOM interference at φ 1 = 0 and φ 1 = π/2, the antibunching central peak arising due to the spatial entanglement, and very fast oscillations around zero path delay, similarly to the two-photon case [19]. The shape of the fast oscillations in the P 22 probability is characterized by a more complicated structure respect to the two-photon case [19], although the oscillation period still equals to the pump wavelength λ p . In particular, Eq.…”

“…A typical tool for creating a spatial entanglement is the well-known two-photon Hong-Ou-Mandel (HOM) interference [19,20,21,22,23], which generates highentangled NOON states with N=2. The NOON states, a class of maximized entangled states, are extremely important in quantum lithography [24] and quantum metrology, due to the possibility of overcoming the standard quantum limit [25].…”

Temporally multimode four-photon Hong-Ou-Mandel interference

“…for the Bell-state measurement [2], it is used to testify the non-locality of entangled system [3] and in quantum lithography [4,5]. Typically this kind of interference is studied by involving two photons in free space, though in the last years integrated quantum devices are also utilized because of their helpful features which allow to manipulate the interference process [6,7].…”