Frontiers in Optics

Integrated path-encoded CNOT quantum gate fabricated by femtosecond laser direct writing

Meng Li, Qian Zhang, Qihuang Gong, Yan Li

Published Jan 1, 2019• 2 citations

Abstract

We demonstrate the fabrication of an integrated path-encoded CNOT quantum gate inside glass using femtosecond laser direct writing. The quantum interference visibility can reach 0.97 and average fidelity of the reconstructed truth table is 0.98.

DOI: 10.1364/fio.2019.jtu4a.51

Related papers

Femtosecond Laser Direct Writing of Integrated Photonic Quantum Chips for Generating Path-Encoded Bell States

Meng Li, Qian Zhang, Yang Chen +3 more

Integrated photonic quantum chip provides a promising platform to perform quantum computation, quantum simulation, quantum metrology and quantum communication. Femtosecond laser direct writing (FLDW) is a potential technique to fabricate various integrated photonic quantum chips in glass. Several quantum logic gates fabricated by FLDW have been reported, such as polarization and path encoded quantum controlled-NOT (CNOT) gates. By combining several single qubit gates and two qubit gates, the quantum circuit can realize different functions, such as generating quantum entangled states and performing quantum computation algorithms. Here we demonstrate the FLDW of integrated photonic quantum chips composed of one Hadamard gate and one CNOT gate for generating all four path-encoded Bell states. The experimental results show that the average fidelity of the reconstructed truth table reaches as high as 98.8 ± 0.3%. Our work is of great importance to be widely applied in many quantum circuits, therefore this technique would offer great potential to fabricate more complex circuits to realize more advanced functions.

MicromachinesDec 15, 202021 citations

Femtosecond laser direct writing of an integrated path-encoded CNOT quantum gate

Qian Zhang, Meng Li, Yang Chen +4 more

Femtosecond lasers enable three-dimensional direct writing of waveguides inside bulk transparent materials and have been applied to the fabrication of integrated photonic quantum logic gates. Up to now, the controlled-NOT (CNOT) gate, the key two-qubit quantum gate, has been realized only for polarization-encoded photonic qubits, which consists of three partially polarizing directional couplers (DCs) or two polarizing DCs. In this work, we demonstrate the femtosecond laser direct writing of a path-encoded CNOT gate formed by five DCs all with precisely controlled splitting ratios and stable symmetric phases inside glass for the first time. The quantum CNOT operation is performed using single photons with an average fidelity higher than 0.98. This provides a novel venue for the fabrication of large-scale 3D quantum computation circuits based on femtosecond laser writing.

Optical Materials ExpressApr 19, 201933 citations

Femtosecond laser direct writing of photonic quantum logic gate chips for generating path-encoded entangled states

Meng Li, Qihuang Gong, Yan Li

Femtosecond laser direct writing (FLDW) technique has been widely applied for fabrications of various photonic quantum chips in glass, such as chips for quantum computation, quantum walk, quantum simulation and quantum metrology. Photonic quantum logic gates are the building blocks for the realization of linear optical universal quantum computation. Up to now, several photonic quantum logic gates have been fabricated by FLDW, such as polarization encoded Hadamard (H) gate, Controlled NOT (CNOT) gate, herald CNOT gate and path encoded herald Controlled phase (CZ) gate and CNOT gate. By combining several single-qubit and two-qubit gates together, the constructed quantum circuits can realize some special functions, such as generating entangled states and perform quantum computation algorithms. Based on the successful fabrication of path encoded CNOT gate by FLDW, we further realized the fabrication of photonic quantum chips by cascading one H gate and one CNOT gate at the control qubit to generate path encoded Bell states, whose fidelity of truth table can reach 97.60.3%. Further, we cascaded one H gate and two parallel CNOT gates at the same control qubit to generate path encoded GHZ states, but which need three photons. Both Bell states and GHZ states are important entangled photon resources, which are widely used in quantum communication and quantum computation, and both combinations of logic gates above can be applied in many quantum circuits, so this work is of great importance and lays the technical foundation for the FLDW of more complex and powerful photonic quantum computation chips.

SPIE Conference on Quantum and Nonlinear OpticsOct 8, 20211 citation

Femtosecond Laser Direct Writing of Path Encoded Two-qubit and Multiqubit Photonic Quantum Gate Chips

Meng Li, Chu Li, Yang Chen +4 more

We demonstrate the first realization of path encoded two-qubit photonic quantum gate chip for generating Bell states, three-qubit Toffoli gate and four-qubit Controlled-Controlled-Controlled NOT gate via combining logic gates together by femtosecond laser direct writing.

Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR)Jan 1, 20220 citations

Femtosecond Laser Direct Writing of Path Encoded Two-qubit and Multiqubit Photonic Quantum Gate Chips

Meng Li, Chu Li, Yang Chen +4 more

We demonstrate the first realization of path encoded two-qubit photonic quantum gate chip for generating Bell states, three-qubit Toffoli gate and four-qubit ControlledControlled-Controlled NOT gate via combining logic gates together by femtosecond laser direct writing.

Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR)Jul 31, 20220 citations

On-chip path encoded photonic quantum Toffoli gate

Meng Li, Chu Li, Yang Chen +12 more

The quantum Toffoli gate is one of the most important three-qubit gates, but it is challenging to construct a chip according to the complicated traditional circuit. Using the optimized 3D configuration with an overpass waveguide to reduce the circuit complexity, we successfully fabricate an on-chip path encoded photonic quantum Toffoli gate enabled by the 3D capability of the femtosecond laser direct writing (FLDW) for the first time to our knowledge, whose truth-table fidelity is higher than 85.5%. Furthermore, a path encoded four-qubit controlled-controlled-controlled NOT gate is written to confirm the scalability of this resource-saving technique. This work paves the way for the FLDW of more complex and powerful photonic quantum computation chips.

Photonics ResearchMay 9, 202243 citations