Entangled resource for interfacing single- and dual-rail optical qubits

Abstract

Today's most widely used method of encoding quantum information in optical qubits is the dual-rail basis, often carried out through the polarisation of a single photon. On the other hand, many stationary carriers of quantum information – such as atoms – couple to light via the single-rail encoding in which the qubit is encoded in the number of photons. As such, interconversion between the two encodings is paramount in order to achieve cohesive quantum networks. In this paper, we demonstrate this by generating an entangled resource between the two encodings and using it to teleport a dual-rail qubit onto its single-rail counterpart. This work completes the set of tools necessary for the interconversion between the three primary encodings of the qubit in the optical field: single-rail, dual-rail and continuous-variable.

On Photonic Implementation of Quantum Computers

“…polarization and path encoding), in which the difference between the logical states consists in the photon occupying one of the two orthogonal optical modes. In this way, the photon is present in any valid state of the qubit, thereby providing an easy way to label loss events, [18].…”

“…This allows easy realisation of single-qubit operations by means of polarisation rotators. In principle, the dual-rail light qubit can be treated as a pair of single-rail qubits carried by each polarisation mode, [18].…”

Tomography of a Feedback Measurement with Photon Detection

“…A scenario where this measurement strategy will be highly beneficial is the discrimination of the two orthogonal superpositions of the vacuum and single photon state, jAEi ¼ ð1= ffiffi ffi 2 p Þðj0i AE j1iÞ. These are the conjugate basis states of the optical single-rail qubit where information is encoded in the photon number of a single optical mode [16][17][18][19][20]. This particular qubit encoding is interesting due to its natural relation to, e.g., atomic and mechanical qubits [21] and its convertibility with cat state qubits and polarization qubits [17][18][19][20].…”

“…These are the conjugate basis states of the optical single-rail qubit where information is encoded in the photon number of a single optical mode [16][17][18][19][20]. This particular qubit encoding is interesting due to its natural relation to, e.g., atomic and mechanical qubits [21] and its convertibility with cat state qubits and polarization qubits [17][18][19][20]. The computational basis states can be distinguished simply by a high-efficiency photodetector, but the states of the conjugate basis are not associated with simple physical observables and can therefore not be directly measured.…”

A new concept for design of photonic integrated circuits with the ultimate density and low loss

“…Alternatively, a CWGA composed of M ≥ 2 N or M ≥ d D waveguides can act as an M dimensional Hilbert space representable by N qubits or D qudits, encoded in 2 and d dimensional vectors, respectively. Finally, the absence of the bend-induced loss avails CWGAs to the singlerail encoding and hence to coupling to the stationary carriers of quantum information [28]. Therefore, the commensurable interconnects can mitigate the downscaling bottleneck irrespectively of the encodings chosen for the future computing paradigm [29].…”