A time-bin qubit entangler using optical switch

Hiroki Takesue

A time-bin qubit is a promising candidate qubit for advanced quantum information processing systems operating over optical fibers or integrated quantum photonic circuits. However, the single- and two-qubit operations of time-bin qubits have been largely unexplored compared with those of polarization qubits. Here, I present a simple scheme for implementing a basic two-qubit operation, namely an ``entangling'' operation of two independent time-bin qubits, based on Hong-Ou-Mandel quantum interference in a high-speed $2\ifmmode\times\else\texttimes\fi{}2$ optical switch. With the proposed scheme, the formation of a time-bin entanglement was confirmed experimentally.

Jennifer Choi

Hsin-Pin Lo, Takuya Ikuta, Nobuyuki Matsuda +2 more

Quantum logic gates are important for quantum computation and quantum information processing in numerous physical systems. Although time-bin qubits are suitable for quantum communication over optical fiber, many essential quantum logic gates for them have not yet been realized. Here, we demonstrated a controlled-phase (C-Phase) gate for time-bin qubits that uses a 2 × 2 optical switch based on an electro-optic modulator. A Hong–Ou–Mandel interference measurement showed that the switch could work as a time-dependent beam splitter with a variable splitting ratio. We confirmed that two independent time-bin qubits were entangled as a result of C-Phase gate operation with the switch.

Gregor Weihs, Tobias Huber, Ana Predojević

Paul G. Kwiat

Hiroki Takesue

I present a simple scheme for entangling two independent time-bin qubits using quantum interference at a high-speed 2×2 optical switch. Non-classical two photon interference fringes were observed experimentally by using the proposed scheme.