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:1109.1762 · Optics Express

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

Xiao-song Ma, Stefan Zotter, Nuray Tetik, Angie Qarry, Thomas Jennewein, Anton Zeilinger

Published Oct 26, 2011• 38 citations
arXivHTMLPDF

Abstract

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.

DOI
10.1364/oe.19.022723

Related papers

Electro-optic modulators for photonic quantum information processing

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

We introduce our recent photonic quantum information processing experiments using the high-speed electro-optic modulator (EOM) based on a lithium niobate waveguides. First, we demonstrated the frequency shifter for single photons by using an optical single sideband (OSSB) modulator, which is based on the nested configuration of four phase modulators (PMs). By properly setting the RF modulation signal and the bias voltage to each PM, we can suppress unwanted sidebands to realize a frequency shifter that can tune the frequency of single photons with accuracy of an RF synthesizer. Using the OSSB modulator, we eliminated the frequency distinguishability between two single photons whose frequencies were different by 25 GHz, and as a result observed a Hong-Ou- Mandel interference with a visibility exceeding 90%. We also proposed and demonstrated a two-qubit controlled logic gate for time-bin qubits using a two-input, two-output optical switch. The switch enables us to individually perform different functions for two temporal bases as a time-dependent beam splitter, so that we can realize controlled-phase (C-Phase) gate for a time-bin qubit. We showed that the states of two separable single photons were entangled as a result of the C-Phase gate operation. We performed the quantum state tomography to obtain density matrices of the output states from the C-Phase gate for some specific input states, and confirmed that the averaged state fidelity to the pure states was 85%. These results indicate that the EOMs will be a useful tool for realizing advanced photonic quantum communication systems.

•Nov 19, 2019•9 citations

Entanglement generation using a controlled-phase gate for time-bin qubits

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.

arXiv:2003.04483•Applied Physics Express•Aug 24, 2018•18 citations

Experimental realization of a 2 × 2 polarization-independent split-ratio-tunable optical beam splitter

Ran Yang, Jian Li, Xiaobo Song +5 more

We realized a polarization-independent split-ratio-tunable optical beam splitter supporting two input and output ports through a stable interferometer. By adjusting the angle of a half-wave plate in the interferometer, we can tune the beam splitter reflectivities for both input ports from 0 to 1, regardless of the input light polarization. High-fidelity polarization-preserving transmission from input to output ports was verified by complete quantum process tomography. Nearly optimal interference effects at the beam splitter with various split ratios were observed by two-photon Hong-Ou-Mandel interference for different input polarization states. Such a beam splitter could find a variety of applications in classical and quantum optical technologies.

Optics Express•Dec 1, 2016•5 citations

Semiconductor-cavity QED-based optical beam splitter

Wen-Xi Lai, Hongcai Li, Xiu Ru Lin +1 more

We theoretically demonstrate that a photonic crystal microcavity coupled to waveguides works as an optical beam splitter. Numerical simulations illustrate that spatially separated two output modes have a relative phase close to $\ensuremath{\pi}/2$ and tunable transmission coefficients. The general transformation of this beam splitter gives a single-qubit rotation operator about the $x$ axis. Using such beam splitters, we show single-photon interference via the Mach-Zehnder interferometer and two-photon entanglement via Hong-Ou-Mandel effect. This system may have great applications in constructing interferometers and integrated circuits for optical quantum information processing with solid-state materials.

Physical Review A•Feb 25, 2009•3 citations

Experimental realization of SWAP operation on hyper-encoded qubits

Robert Stárek, Martina Miková, Ivo Straka +4 more

Hyper-encoding enables storing several qubits in a single photon using its different degrees of freedom like polarization and spatial ones. This approach enables feasible implementation of multi-qubit operations. One of the basic manipulations of two or more qubits is to swap their quantum state. Here we report on feasible and stable experimental implementation of a deterministic single photon two-qubit SWAP gate that interchanges path and polarization qubits. We discuss the principle of its operation and give detailed information about experimental demonstration employing two Mach-Zehnder interferometers with one common arm. The gate characterization is done by full quantum process tomography using photons produced by heralded single-photon source. The achieved quantum process fidelity reached more than 0.94 with an effective phase uncertainty of the whole setup, evaluated by means of Allan deviation, below 2.5 deg for 2.5 h without any active stabilization. Our design provides a contribution to the hyper-encoded linear quantum optics toolbox.

Optics Express•Mar 23, 2018•22 citations

Tunable coherent microwave beam splitter and combiner at the single-photon level

Y.-H. Huang, Kaun-Chun Hsieh, F. Aziz +10 more

A beam splitter is a key component used to direct and combine light paths in various optical and microwave systems. It plays a crucial role in devices like interferometers, such as the Mach–Zehnder and Hong–Ou–Mandel setups, where it splits light into different paths for interference measurements. These measurements are vital for precise phase and coherence testing in both classical and quantum optical experiments. In this work, we present a nonlinear beam splitter and beam combiner utilizing a frequency-tunable superconducting artificial atom in a one-dimensional open waveguide. Probed with coherent states at the single-photon level (average photon number ⟨N⟩ ≪1), this device demonstrates highly tunable transparency, ranging from near unity to complete reflection. Additionally, the beam combiner can merge two coherent beams, generating interference fringes as the relative phase between them varies.

arXiv:2503.20353•Applied Physics Letters•Jul 7, 2025•2 citations
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.
We introduce our recent photonic quantum information processing experiments using the high-speed electro-optic modulator (EOM) based on a lithium niobate waveguides. First, we demonstrated the frequency shifter for single photons by using an optical single sideband (OSSB) modulator, which is based on the nested configuration of four phase modulators (PMs). By properly setting the RF modulation signal and the bias voltage to each PM, we can suppress unwanted sidebands to realize a frequency shifter that can tune the frequency of single photons with accuracy of an RF synthesizer. Using the OSSB modulator, we eliminated the frequency distinguishability between two single photons whose frequencies were different by 25 GHz, and as a result observed a Hong-Ou- Mandel interference with a visibility exceeding 90%. We also proposed and demonstrated a two-qubit controlled logic gate for time-bin qubits using a two-input, two-output optical switch. The switch enables us to individually perform different functions for two temporal bases as a time-dependent beam splitter, so that we can realize controlled-phase (C-Phase) gate for a time-bin qubit. We showed that the states of two separable single photons were entangled as a result of the C-Phase gate operation. We performed the quantum state tomography to obtain density matrices of the output states from the C-Phase gate for some specific input states, and confirmed that the averaged state fidelity to the pure states was 85%. These results indicate that the EOMs will be a useful tool for realizing advanced photonic quantum communication systems.
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.
We realized a polarization-independent split-ratio-tunable optical beam splitter supporting two input and output ports through a stable interferometer. By adjusting the angle of a half-wave plate in the interferometer, we can tune the beam splitter reflectivities for both input ports from 0 to 1, regardless of the input light polarization. High-fidelity polarization-preserving transmission from input to output ports was verified by complete quantum process tomography. Nearly optimal interference effects at the beam splitter with various split ratios were observed by two-photon Hong-Ou-Mandel interference for different input polarization states. Such a beam splitter could find a variety of applications in classical and quantum optical technologies.
We theoretically demonstrate that a photonic crystal microcavity coupled to waveguides works as an optical beam splitter. Numerical simulations illustrate that spatially separated two output modes have a relative phase close to $\ensuremath{\pi}/2$ and tunable transmission coefficients. The general transformation of this beam splitter gives a single-qubit rotation operator about the xxx axis. Using such beam splitters, we show single-photon interference via the Mach-Zehnder interferometer and two-photon entanglement via Hong-Ou-Mandel effect. This system may have great applications in constructing interferometers and integrated circuits for optical quantum information processing with solid-state materials.
Hyper-encoding enables storing several qubits in a single photon using its different degrees of freedom like polarization and spatial ones. This approach enables feasible implementation of multi-qubit operations. One of the basic manipulations of two or more qubits is to swap their quantum state. Here we report on feasible and stable experimental implementation of a deterministic single photon two-qubit SWAP gate that interchanges path and polarization qubits. We discuss the principle of its operation and give detailed information about experimental demonstration employing two Mach-Zehnder interferometers with one common arm. The gate characterization is done by full quantum process tomography using photons produced by heralded single-photon source. The achieved quantum process fidelity reached more than 0.94 with an effective phase uncertainty of the whole setup, evaluated by means of Allan deviation, below 2.5 deg for 2.5 h without any active stabilization. Our design provides a contribution to the hyper-encoded linear quantum optics toolbox.
A beam splitter is a key component used to direct and combine light paths in various optical and microwave systems. It plays a crucial role in devices like interferometers, such as the Mach–Zehnder and Hong–Ou–Mandel setups, where it splits light into different paths for interference measurements. These measurements are vital for precise phase and coherence testing in both classical and quantum optical experiments. In this work, we present a nonlinear beam splitter and beam combiner utilizing a frequency-tunable superconducting artificial atom in a one-dimensional open waveguide. Probed with coherent states at the single-photon level (average photon number ⟨N⟩ ≪1), this device demonstrates highly tunable transparency, ranging from near unity to complete reflection. Additionally, the beam combiner can merge two coherent beams, generating interference fringes as the relative phase between them varies.