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

Conference on Lasers and Electro-Optics

Temporal-mode tomography of single photons

Vahid Ansari, Markus Allgaier, Linda Sansoni, Benjamin Brecht, Jonathan Roslund, Nicolas Treps, Georg Harder, Christine Silberhorn

Published Jan 1, 2017• 6 citations
Publisher

Abstract

Accessing a high dimensional Hilbert space spanned by temporal modes (TMs) of single-photons is an intriguing idea for quantum information protocols, though it is experimentally challenging. The quantum pulse gate (QPG), a group-velocity matched sum-frequency process, can perform arbitrary TM resolved measurement. We present a thorough characterisation of measurement operators of a QPG and we show that this device is capable of performing full state tomography with 99% fidelity. Moreover, we use this device for TM tomography of pure and mixed heralded single-photon states in 7-dimensional Hilbert space.

DOI
10.1364/cleo_qels.2017.fth4e.4

Related papers

Temporal-mode measurement tomography of a quantum pulse gate

Vahid Ansari, Georg Harder, Markus Allgaier +2 more

Encoding quantum information in the photon temporal mode (TM) offers a robust platform for high-dimensional quantum protocols. The main practical challenge, however, is to design a device that operates on single photons in specific TMs and all coherent superpositions. The quantum pulse gate (QPG) is a mode-selective sum-frequency generation designed for this task. Here, we perform a full modal characterization of a QPG using weak coherent states in well-defined TMs. We reconstruct a full set of measurement operators, which show an average fidelity of 0.85 to a theoretically ideal device when operating on a seven-dimensional space. Then we use these characterized measurement operators of the QPG to calibrate the device. Using the calibrated device and a tomographically complete set of measurements, we show that the QPG can perform high-dimensional TM state tomography with 0.99 fidelity.

arXiv:1702.03336•Physical Review A•Dec 13, 2017•53 citations

Realization of a Multi-Output Quantum Pulse Gate for Decoding High-Dimensional Temporal Modes of Single-Photon States

Laura Serino, Jano Gil-López, Michael Stefszky +4 more

Temporal modes (TMs) of photons provide an appealing high-dimensional encoding basis for quantum information.While techniques to generate TM states have been established, high-dimensional decoding of single-photon TMs remains an open challenge.In this work, we experimentally demonstrate demultiplexing of five-dimensional TMs of single photons with an average fidelity of 0.96 ± 0.01, characterized via measurement tomography.This is achieved with use of a newly developed device, the multi-output quantum pulse gate (MQPG).We demonstrate a proof-of-principle complete decoder based on the MQPG that operates on any basis from a set of six five-dimensional mutually unbiased bases and is therefore suitable as a receiver for high-dimensional quantum key distribution.Furthermore, we confirm the highquality operation of the MQPG by performing resource-efficient state tomography with an average fidelity of 0.98 ± 0.02.

arXiv:2211.05693•PRX Quantum•Apr 12, 2023•58 citations

Multi-Output Quantum Pulse Gate: a High-Dimensional Temporal-Mode Decoder

Laura Serino, Jano Gil-López, Michael Stefszky +4 more

We demonstrate a temporal-mode decoder based on a multi-output quantum pulse gate. Measurement tomography on a complete set of five-dimensional mutually unbiased bases confirms single-photon-level operation at telecom wavelengths with an average fidelity of 96%.

Frontiers in Optics•Jan 1, 2022•0 citations

High-dimensional temporal-mode decoding with a multi-output quantum pulse gate

Laura Serino, Jano Gil-López, Werner Ridder +4 more

We demonstrate a multi-output quantum pulse gate that sorts temporal modes (or their superpositions) at telecommunication wavelengths into separate output channels. This device will prove beneficial for high-dimensional quantum information processing in the time-frequency domain.

Quantum Information and Measurement (QIM)•Jan 1, 2021•2 citations

Self-guided tomography of time-frequency qudits

Laura Serino, Markus Rambach, Benjamin Brecht +2 more

Abstract High-dimensional time-frequency encodings have the potential to significantly advance quantum information science; however, practical applications require precise knowledge of the encoded quantum states, which becomes increasingly challenging for larger Hilbert spaces. Self-guided tomography (SGT) has emerged as a practical and scalable technique for this purpose in the spatial domain. Here, we apply SGT to estimate time-frequency states using a multi-output quantum pulse gate. We achieve fidelities of more than 99% for 3- and 5-dimensional states without the need for calibration or post-processing. We demonstrate the robustness of SGT against statistical and environmental noise, highlighting its efficacy in the photon-starved regime typical of quantum information applications.

arXiv:2411.19277•Quantum Science and Technology•Jan 31, 2025•2 citations

Tailoring nonlinear processes for quantum optics with pulsed temporal-mode encodings

Vahid Ansari, John M. Donohue, Benjamin Brecht +1 more

The time-frequency degree of freedom is a powerful resource for implementing high-dimensional quantum information processing. In particular, field-orthogonal pulsed temporal modes offer a flexible framework compatible with both long-distance fibre networks and integrated waveguide devices. In order for this architecture to be fully utilised, techniques to reliably generate diverse quantum states of light and accurately measure complex temporal waveforms must be developed. To this end, nonlinear processes mediated by spectrally shaped pump pulses in group-velocity engineered waveguides and crystals provide a capable toolbox. In this review, we examine how tailoring the phasematching conditions of parametric downconversion and sum-frequency generation allows for highly pure single-photon generation, flexible temporal-mode entanglement, and accurate measurement of time-frequency photon states. We provide an overview of experimental progress towards these goals, and summarise challenges that remain in the field.

arXiv:1803.04316•Optica•Apr 30, 2018•152 citations
Accessing a high dimensional Hilbert space spanned by temporal modes (TMs) of single-photons is an intriguing idea for quantum information protocols, though it is experimentally challenging. The quantum pulse gate (QPG), a group-velocity matched sum-frequency process, can perform arbitrary TM resolved measurement. We present a thorough characterisation of measurement operators of a QPG and we show that this device is capable of performing full state tomography with 99% fidelity. Moreover, we use this device for TM tomography of pure and mixed heralded single-photon states in 7-dimensional Hilbert space.
Encoding quantum information in the photon temporal mode (TM) offers a robust platform for high-dimensional quantum protocols. The main practical challenge, however, is to design a device that operates on single photons in specific TMs and all coherent superpositions. The quantum pulse gate (QPG) is a mode-selective sum-frequency generation designed for this task. Here, we perform a full modal characterization of a QPG using weak coherent states in well-defined TMs. We reconstruct a full set of measurement operators, which show an average fidelity of 0.85 to a theoretically ideal device when operating on a seven-dimensional space. Then we use these characterized measurement operators of the QPG to calibrate the device. Using the calibrated device and a tomographically complete set of measurements, we show that the QPG can perform high-dimensional TM state tomography with 0.99 fidelity.
Temporal modes (TMs) of photons provide an appealing high-dimensional encoding basis for quantum information.While techniques to generate TM states have been established, high-dimensional decoding of single-photon TMs remains an open challenge.In this work, we experimentally demonstrate demultiplexing of five-dimensional TMs of single photons with an average fidelity of 0.96 ± 0.01, characterized via measurement tomography.This is achieved with use of a newly developed device, the multi-output quantum pulse gate (MQPG).We demonstrate a proof-of-principle complete decoder based on the MQPG that operates on any basis from a set of six five-dimensional mutually unbiased bases and is therefore suitable as a receiver for high-dimensional quantum key distribution.Furthermore, we confirm the highquality operation of the MQPG by performing resource-efficient state tomography with an average fidelity of 0.98 ± 0.02.
Abstract High-dimensional time-frequency encodings have the potential to significantly advance quantum information science; however, practical applications require precise knowledge of the encoded quantum states, which becomes increasingly challenging for larger Hilbert spaces. Self-guided tomography (SGT) has emerged as a practical and scalable technique for this purpose in the spatial domain. Here, we apply SGT to estimate time-frequency states using a multi-output quantum pulse gate. We achieve fidelities of more than 99% for 3- and 5-dimensional states without the need for calibration or post-processing. We demonstrate the robustness of SGT against statistical and environmental noise, highlighting its efficacy in the photon-starved regime typical of quantum information applications.
The time-frequency degree of freedom is a powerful resource for implementing high-dimensional quantum information processing. In particular, field-orthogonal pulsed temporal modes offer a flexible framework compatible with both long-distance fibre networks and integrated waveguide devices. In order for this architecture to be fully utilised, techniques to reliably generate diverse quantum states of light and accurately measure complex temporal waveforms must be developed. To this end, nonlinear processes mediated by spectrally shaped pump pulses in group-velocity engineered waveguides and crystals provide a capable toolbox. In this review, we examine how tailoring the phasematching conditions of parametric downconversion and sum-frequency generation allows for highly pure single-photon generation, flexible temporal-mode entanglement, and accurate measurement of time-frequency photon states. We provide an overview of experimental progress towards these goals, and summarise challenges that remain in the field.