Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2405.10154

Quantum CZ Gate based on Single Gradient Metasurface

Liu, Qi, Yu Tian, Zhaohua Tian, Guixin Li, Xi‐Feng Ren, Qihuang Gong, Ying Gu

Published May 16, 2024• 0 citations
arXivHTMLPDF

Abstract

We propose a scheme to realize quantum controlled-Z (CZ) gates through single gradient metasurface. Using its unique parallel beam-splitting feature, i.e., a series of connected beam splitters with the same splitting ratio, one metasurface can support a CZ gate, several independent CZ gates, or a cascaded CZ gates. Taking advantage of the input polarization determined output path-locking feature, both polarization-encoded and path-encoded CZ gates can be demonstrated on the same metasurface, which further improves the integration level of quantum devices. Our research paves the way for integrating quantum logical function through the metasurface.

DOI
10.48550/arxiv.2405.10154

Related papers

Quantum CZ gates on a single gradient metasurface

Qi Liu, Yu Tian, Zhaohua Tian +5 more

For the requirement of quantum photonic integration in on-chip quantum information, we propose a scheme to realize quantum controlled-Z (CZ) gates through single gradient metasurface. Using its parallel beam-splitting feature, i.e., a series of connected beamsplitters with the same splitting ratio, one metasurface can support a polarization encoding CZ gate or path encoding CZ gate, several independent CZ gates, and cascade CZ gates. Taking advantage that the path of output state is locked by the polarization of input state, path encoding CZ gates can efficiently filter out bit-flip errors coming from beam-splitting processes. These CZ gates also have the potential to detect quantum errors and generate high-dimensional entanglement through multi-degree-of-freedom correlation on metasurfaces. By integrating quantum CZ gates into a single metasurface, our results open an avenue for high-density and multifunctional integration of quantum devices.

Light Science & Applications•May 13, 2025•7 citations

Cascadable Quantum Controlled-Z Gates on a Single Metasurface

Ying Gu, Qi Liu, Yu Tian +5 more

We theoretically demonstrate several cascadable quantum controlled-Z gates on a single metasurface by utilizing its parallel beam-splitting capability, which is valid for both polarization and path-encoding qubits. The path-encoding case can filter out bit-flip errors.

•Jan 1, 2025•0 citations

A Parallel Beam Splitting Based on Gradient Metasurface: Preparation and Fusion of Quantum Entanglement

Qi Liu, Xuan Liu, Yü Tian +5 more

Gradient metasurface, formed by a set of subwavelength unit cells with different phase modulation, is widely used in polarized beam splitting (BS) in the classical and quantum optics. Specifically, its phase gradient allows the path and polarization of multiple output lights to be locked by corresponding inputs.Using this unique path-polarization locked property, we demonstrate that the single metasurface can function as sequentially linked beamsplitters, enabling the parallelization of a series of BS processes. Such a parallel BS metasurface provides a multi-beam interference capability for both classical and quantum light manipulation. Taking this advantage, we first prepare path and polarization hybrid entangled states of two, three, and multi photons from unentangled photon sources. Then, the ability of parallel BS-facilitated entanglement is applied to demonstrate entanglement fusion among entangled photon pairs, which can greatly enlarge the entanglement dimension. The principle of parallel BS through the metasurface opens up a versatile way to manipulate the quantum state at the micro/nano scale, which will have potential applications in on-chip quantum optics and quantum information processing.

arXiv:2403.08233•Mar 13, 2024•0 citations

High-fidelity single-layer gradient metasurface for optical quantum controlled-Y gate

Dongyan Li, Weihao Zhang, Yaru Li +1 more

Abstract Two-qubit controlled gates such as the controlled-Y (CY) gate are essential building blocks for universal quantum computation. While linear-optical implementations of controlled-NOT and controlled-Z gates have been realized with discrete optics and integrated waveguides, realizing a faithful CY gate on a compact, single-element platform remains challenging because it requires both a controlled bit-flip and precise ± i phase factors. Here we propose and numerically demonstrate an optical quantum CY gate based on a single-layer Pancharatnam–Berry gradient metasurface operating at 1550 nm. Polarization-encoded photons are processed by a 26-pillar amorphous-silicon supercell that realizes parallel beam splitting, diffraction routing and two-photon interference. After fixed local polarization encoding/analysis transformations and coincidence post-selection, the reconstructed two-photon gate matrix matches the ideal CY unitary with a matrix fidelity of 0.9885. Computational ZZ- and complementary XY-basis truth tables yield fidelities of 0.9902 and 0.9924, respectively, while the four phase-type Bell states generated by the gate exhibit an average fidelity of 0.9902. The average post-selection success probability extracted from full-wave simulations is 0.0976. Wavelength-dependent simulations including material dispersion indicate a simulated bandwidth of approximately 26.5 nm ( F CY ⩾ 0.95 ). The results establish a compact, monolithic metasurface platform for phase-sensitive controlled quantum logic and entangled-state manipulation.

Quantum Science and Technology•Aug 25, 2026•0 citations

Multiphoton path-polarization entanglement through a single gradient metasurface

Qi Liu, Xuan Liu, Yu Tian +5 more

Multiphoton entanglement with high information capacity plays an essential role in quantum information processing. The appearance of parallel beam splitting (BS) in a gradient metasurface provides the chance to prepare the multiphoton entanglement in one step. Here, we use a single metasurface to construct multiphoton path-polarization entanglement. Based on the parallel BS property, entanglement among N unentangled photons is created after they pass through a gradient metasurface. Also, with this ability, entanglement fusion among several pairs of entangled photons is set up, which can greatly enlarge the entanglement dimension. These theoretical results pave the way for manipulating metasurface-based multiphoton entanglement, which holds great promise for ultracompact on-chip quantum information processing.

Advanced Photonics Nexus•Feb 13, 2025•9 citations

A high-speed tunable beam splitter for feed-forward photonic quantum information processing

Xiao-song Ma, Stefan Zotter, Nuray Tetik +3 more

We realize quantum gates for path qubits with a high-speed, polarization-independent and tunable beam splitter. Two electro-optical modulators act in a Mach-Zehnder interferometer as high-speed phase shifters and rapidly tune its splitting ratio. We test its performance with heralded single photons, observing a polarization-independent interference contrast above 95%. The switching time is about 5.6 ns, and a maximal repetition rate is 2.5 MHz. We demonstrate tunable feed-forward operations of a single-qubit gate of path-encoded qubits and a two-qubit gate via measurement-induced interaction between two photons.

arXiv:1109.1762•Optics Express•Oct 26, 2011•38 citations
We propose a scheme to realize quantum controlled-Z (CZ) gates through single gradient metasurface. Using its unique parallel beam-splitting feature, i.e., a series of connected beam splitters with the same splitting ratio, one metasurface can support a CZ gate, several independent CZ gates, or a cascaded CZ gates. Taking advantage of the input polarization determined output path-locking feature, both polarization-encoded and path-encoded CZ gates can be demonstrated on the same metasurface, which further improves the integration level of quantum devices. Our research paves the way for integrating quantum logical function through the metasurface.
For the requirement of quantum photonic integration in on-chip quantum information, we propose a scheme to realize quantum controlled-Z (CZ) gates through single gradient metasurface. Using its parallel beam-splitting feature, i.e., a series of connected beamsplitters with the same splitting ratio, one metasurface can support a polarization encoding CZ gate or path encoding CZ gate, several independent CZ gates, and cascade CZ gates. Taking advantage that the path of output state is locked by the polarization of input state, path encoding CZ gates can efficiently filter out bit-flip errors coming from beam-splitting processes. These CZ gates also have the potential to detect quantum errors and generate high-dimensional entanglement through multi-degree-of-freedom correlation on metasurfaces. By integrating quantum CZ gates into a single metasurface, our results open an avenue for high-density and multifunctional integration of quantum devices.
Gradient metasurface, formed by a set of subwavelength unit cells with different phase modulation, is widely used in polarized beam splitting (BS) in the classical and quantum optics. Specifically, its phase gradient allows the path and polarization of multiple output lights to be locked by corresponding inputs.Using this unique path-polarization locked property, we demonstrate that the single metasurface can function as sequentially linked beamsplitters, enabling the parallelization of a series of BS processes. Such a parallel BS metasurface provides a multi-beam interference capability for both classical and quantum light manipulation. Taking this advantage, we first prepare path and polarization hybrid entangled states of two, three, and multi photons from unentangled photon sources. Then, the ability of parallel BS-facilitated entanglement is applied to demonstrate entanglement fusion among entangled photon pairs, which can greatly enlarge the entanglement dimension. The principle of parallel BS through the metasurface opens up a versatile way to manipulate the quantum state at the micro/nano scale, which will have potential applications in on-chip quantum optics and quantum information processing.
Abstract Two-qubit controlled gates such as the controlled-Y (CY) gate are essential building blocks for universal quantum computation. While linear-optical implementations of controlled-NOT and controlled-Z gates have been realized with discrete optics and integrated waveguides, realizing a faithful CY gate on a compact, single-element platform remains challenging because it requires both a controlled bit-flip and precise ± i phase factors. Here we propose and numerically demonstrate an optical quantum CY gate based on a single-layer Pancharatnam–Berry gradient metasurface operating at 1550 nm. Polarization-encoded photons are processed by a 26-pillar amorphous-silicon supercell that realizes parallel beam splitting, diffraction routing and two-photon interference. After fixed local polarization encoding/analysis transformations and coincidence post-selection, the reconstructed two-photon gate matrix matches the ideal CY unitary with a matrix fidelity of 0.9885. Computational ZZ- and complementary XY-basis truth tables yield fidelities of 0.9902 and 0.9924, respectively, while the four phase-type Bell states generated by the gate exhibit an average fidelity of 0.9902. The average post-selection success probability extracted from full-wave simulations is 0.0976. Wavelength-dependent simulations including material dispersion indicate a simulated bandwidth of approximately 26.5 nm ( F CY ⩾ 0.95 ). The results establish a compact, monolithic metasurface platform for phase-sensitive controlled quantum logic and entangled-state manipulation.
Multiphoton entanglement with high information capacity plays an essential role in quantum information processing. The appearance of parallel beam splitting (BS) in a gradient metasurface provides the chance to prepare the multiphoton entanglement in one step. Here, we use a single metasurface to construct multiphoton path-polarization entanglement. Based on the parallel BS property, entanglement among N unentangled photons is created after they pass through a gradient metasurface. Also, with this ability, entanglement fusion among several pairs of entangled photons is set up, which can greatly enlarge the entanglement dimension. These theoretical results pave the way for manipulating metasurface-based multiphoton entanglement, which holds great promise for ultracompact on-chip quantum information processing.
We realize quantum gates for path qubits with a high-speed, polarization-independent and tunable beam splitter. Two electro-optical modulators act in a Mach-Zehnder interferometer as high-speed phase shifters and rapidly tune its splitting ratio. We test its performance with heralded single photons, observing a polarization-independent interference contrast above 95%. The switching time is about 5.6 ns, and a maximal repetition rate is 2.5 MHz. We demonstrate tunable feed-forward operations of a single-qubit gate of path-encoded qubits and a two-qubit gate via measurement-induced interaction between two photons.