Optimal quantum cloning of orbital angular momentum photon qubits through Hong–Ou–Mandel coalescence

Abstract

The orbital angular momentum (OAM) of light, associated with a helical structure of the wavefunction, has great potential in quantum photonics, as it allows a higher dimensional quantum space to be attached to each photon. Hitherto, however, the use of OAM has been hindered by difficulties in its manipulation. Here, by making use of the recently demonstrated spin-OAM information transfer tools, we report the first observation of the Hong–Ou–Mandel coalescence of two incoming photons having non-zero OAM into the same outgoing mode of a beamsplitter. The coalescence can be switched on and off by varying the input OAM state of the photons. Such an effect has then been used to carry out the 1 -> 2 universal optimal quantum cloning of OAM-encoded qubits, using the symmetrization technique already developed for polarization. These results are shown to be scalable to quantum spaces of arbitrary dimensions, even combining different degrees of freedom of the photons

Complete experimental toolbox for alignment-free quantum communication

“…Specifically, each photon suffers a variation in its OAM by an amount ∆ = 2 s q z p determined by the charge q and the SAM s z p of the input polarization. q-plates with q = 1 have been recently used to demonstrate interesting spin-OAM quantum information manipulations [29][30][31][32][33] .…”

Hybrid entanglement swapping of photons: Creating the orbital angular momentum Bell states and Greenberger-Horne-Zeilinger states

“…1(a) and such q-plates can be made by photoaligned liquid crystal polymers [24]. Based on q-plates, increase of Shannon dimensionality [25], entanglement transfer from spin to OAM [26], and quantum cloning of OAM qubits [27] or spin-orbit ququarts [28] were recently reported. In the single photon space, the function of a q-plate is visualized by Fig.…”

Polarization-based control of spin-orbit vector modes of light in biphoton interference

“…Although a number of works have studied biphoton interference involving the spin and/or orbital degrees of freedom (e.g. [32][33][34]), this phenomenon has, to our knowledge, yet to be realized for output photons sharing field modes whose internal degrees of freedom are nonseparable. Potential applications of the tunable vector mode structures discussed in this work involve their use in spatially inhomogeneous light-matter interactions which depend on the polarization degree of freedom of light, including the design of dynamic optical tweezers on the classical beam level, and interactions with atomic systems involving biphoton states of light in structured vector modes.…”