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

New Journal of Physics

Reconstruction of single-photon emission with a self-calibrated wQED device based on a transmon qubit

Danilo Labranca, Adam J. Sirois, Manuel A. Castellanos-Beltran, David I. Olaya, Samuel P. Benz, Andrea Giachero, P. F. Hopkins

Published Jun 23, 2025• 0 citations
Publisher

Abstract

Abstract We present a detailed study of a microwave single-photon source utilizing a transmon qubit asymmetrically coupled to two transmission lines: a weakly coupled drive line and a strongly coupled emission line. Our design allows for the generation of single photons in the microwave regime, which are essential for quantum communication, computing, and sensing applications. In addition to single-photon generation, the same design functions as a power sensor and enables precise measurement of the system’s attenuation. This dual functionality allows us to calibrate the noise of our amplification chain. This enables a self-calibrated architecture in which the same device acts simultaneously as the photon source and as a reference standard, eliminating the need for external tones or calibrated inputs. With this calibration we reconstruct the density matrix of the emitted photon state, for which we achieve a fidelity of 61.4% and measure a second-order correlation function of g ( 2 ) ( 0 ) = 0.06 − 0.06 + 0.45 , indicating quantum nature and single-photon characteristics. These results confirm generation of single photons and demonstrate the potential of transmon qubits in advancing quantum technologies in the microwave domain.

DOI
10.1088/1367-2630/ade736

Related papers

Quantum efficiency, purity and stability of a tunable, narrowband microwave single-photon source

Yong Lu, Andreas Bengtsson, Jonathan Burnett +7 more

Abstract We demonstrate an on-demand source of microwave single photons with 71–99% intrinsic quantum efficiency. The source is narrowband (300 kHz) and tuneable over a 600 MHz range around 5.2 GHz. Such a device is an important element in numerous quantum technologies and applications. The device consists of a superconducting transmon qubit coupled to the open end of a transmission line. A π-pulse excites the qubit, which subsequently rapidly emits a single photon into the transmission line. A cancellation pulse then suppresses the reflected π-pulse by 33.5 dB, resulting in 0.005 photons leaking into the photon emission channel. We verify strong antibunching of the emitted photon field and determine its Wigner function. Non-radiative decay and 1/f flux noise both affect the quantum efficiency. We also study the device stability over time and identify uncorrelated discrete jumps of the pure dephasing rate at different qubit frequencies on a time scale of hours, which we attribute to independent two-level system defects in the device dielectrics, dispersively coupled to the qubit. Our single-photon source with only one input port is more compact and scalable compared to standard implementations.

arXiv:2105.11234•npj Quantum Information•Sep 23, 2021•24 citations

Tunable Microwave Single-Photon Source Based on Transmon Qubit with High Efficiency

Yu Zhou, Zhihui Peng, Yuta Horiuchi +2 more

Single-photon sources are of great interest because they are key elements in different promising applications of quantum technologies. Here we demonstrate a highly efficient tunable on-demand microwave single-photon source based on a transmon qubit with an intrinsic emission efficiency above $98\mathrm{%}$. The high efficiency ensures a negligible pure dephasing rate and the necessary conditions for generation of indistinguishable photons. We provide an extended discussion and analysis of the efficiency of the photon generation. To further experimentally confirm the single-photon property of the source, correlation functions of the emission field are also measured using linear detectors with a GPU-enhanced signal-processing technique. Our results experimentally demonstrate that frequency tunability and negligible pure dephasing rate can be achieved simultaneously and show that such a tunable single-photon source can be good for various practical applications in quantum communication, simulations and information processing in the microwave regime.

arXiv:1905.04032•Physical Review Applied•Mar 3, 2020•42 citations

Tuneable on-demand single-photon source in the microwave range

Zhihui Peng, Sebastian E. de Graaf, J. S. Tsai +1 more

An on-demand single-photon source is a key element in a series of prospective quantum technologies and applications. Here we demonstrate the operation of a tuneable on-demand microwave photon source based on a fully controllable superconducting artificial atom strongly coupled to an open-ended transmission line. The atom emits a photon upon excitation by a short microwave π-pulse applied through a control line. The intrinsically limited device efficiency is estimated to be in the range 65-80% in a wide frequency range from 7.75 to 10.5 GHz continuously tuned by an external magnetic field. The actual demonstrated efficiency is also affected by the excited state preparation, which is about 90% in our experiments. The single-photon generation from the single-photon source is additionally confirmed by anti-bunching in the second-order correlation function. The source may have important applications in quantum communication, quantum information processing and sensing.

arXiv:1505.05614•Nature Communications•Aug 22, 2016•111 citations

Efficient Tunable Microwave Single-photon Source Based on Transmon Qubit

Yu Zhou, Zhihui Peng, Yuta Horiuchi +2 more

Single-photon sources of high efficiency are of great interest because they are the key elements in many prospective quantum technologies and applications. Based on our previous work, here we demonstrate a high-quality tunable microwave single-photon source based on transmon qubit with intrinsic emission efficiency more than 99%. To further confirm the single-photon property of the source, we study the single-photon interference in a Hanbury-Brown-Twiss (HBT) type setup and measure the correlation functions of the emission field using linear detectors with GPU-enhanced signal processing technique. The antibunching in second-order correlation function is clearly observed. The theoretical calculations agree well with the experimental results. Such a high-quality single-photon source may be used as a building block for quantum communication, simulation and information processing in microwave regime.

IEEE International Superconductive Electronics Conference (ISEC)•Jul 1, 2019•2 citations

Transmon Architecture for Emission and Detection of Single Microwave Photons

Daniel L. Campbell, Stephen McCoy, Melinda Andrews +12 more

We develop a compact transmon emitter/detector (TED) superconducting circuit and demonstrate its dual functionality as a single-photon source and detector. In our setup, photons emitted by a source TED are transmitted via a meter-long coaxial cable, routed through a circulator, and captured by a measurement TED. Both TED modules operate with nominally identical parameters, highlighting the flexibility of this novel architecture. Furthermore, we introduce an efficient microwave photon detection scheme tailored to the TED. Using this setup, we detect 60% of the emitted Fock state photons and infer a 95% detection efficiency at the input of the measurement TED, which we calibrate against coherent state measurements. The reset and photon emission/detection processes each require approximately $2\,μs$, yielding a minimum protocol duration of $4\,μs$ as constrained by our chosen TED parameters. Ultimately, the TED demonstrates a new use case for the recently developed double transmon coupler (DTC): a compact, drop-in, tunable, and transition-selective link between a coherent data transmon and a waveguide. Circuits like the TED will play a vital role in quantum information processing by facilitating unconditional fast reset, enabling microwave photon metrology, and serving as nascent quantum communication interfaces (QCIs). QCIs mediate entanglement distribution between quantum processing units (QPUs) within a cryostat or interface with microwave-to-optical transducers for long-range quantum networking.

quant-pharXiv:2601.11378•Jan 19, 2026•0 citations

Generation of Frequency-Tunable Shaped Single Microwave Photons Using a Fixed-Frequency Superconducting Qubit

Takeaki Miyamura, Yoshiki Sunada, Zhiling Wang +3 more

Scaling up a superconducting quantum computer will likely require quantum communication between remote chips, which can be implemented using an itinerant microwave photon in a transmission line. To realize high-fidelity communication, it is essential to control the frequency and temporal shape of the microwave photon. In this work, we demonstrate the generation of frequency-tunable shaped microwave photons without resorting to any frequency-tunable circuit element. We develop a framework that treats a microwave resonator as a band-pass filter mediating the interaction between a superconducting qubit and the modes in the transmission line. This interpretation allows us to stimulate the photon emission by an off-resonant drive signal. We characterize how the frequency and temporal shape of the generated photon depends on the frequency and amplitude of the drive signal. By modulating the drive amplitude and frequency, we achieve a frequency tunability of 40 MHz while maintaining the photon mode shape time symmetric. Through measurements of the quadrature amplitudes of the emitted photons, we demonstrate a consistently high state and process fidelities around 95% across the tunable frequency range. Our hardware-efficient approach eliminates the need for additional biasing lines typically required for frequency tuning, offering a simplified architecture for scalable quantum communication.

arXiv:2503.05536•PRX Quantum•Jun 9, 2025•5 citations
Abstract We present a detailed study of a microwave single-photon source utilizing a transmon qubit asymmetrically coupled to two transmission lines: a weakly coupled drive line and a strongly coupled emission line. Our design allows for the generation of single photons in the microwave regime, which are essential for quantum communication, computing, and sensing applications. In addition to single-photon generation, the same design functions as a power sensor and enables precise measurement of the system’s attenuation. This dual functionality allows us to calibrate the noise of our amplification chain. This enables a self-calibrated architecture in which the same device acts simultaneously as the photon source and as a reference standard, eliminating the need for external tones or calibrated inputs. With this calibration we reconstruct the density matrix of the emitted photon state, for which we achieve a fidelity of 61.4% and measure a second-order correlation function of g ( 2 ) ( 0 ) = 0.06 − 0.06 + 0.45 , indicating quantum nature and single-photon characteristics. These results confirm generation of single photons and demonstrate the potential of transmon qubits in advancing quantum technologies in the microwave domain.
Abstract We demonstrate an on-demand source of microwave single photons with 71–99% intrinsic quantum efficiency. The source is narrowband (300 kHz) and tuneable over a 600 MHz range around 5.2 GHz. Such a device is an important element in numerous quantum technologies and applications. The device consists of a superconducting transmon qubit coupled to the open end of a transmission line. A π-pulse excites the qubit, which subsequently rapidly emits a single photon into the transmission line. A cancellation pulse then suppresses the reflected π-pulse by 33.5 dB, resulting in 0.005 photons leaking into the photon emission channel. We verify strong antibunching of the emitted photon field and determine its Wigner function. Non-radiative decay and 1/f flux noise both affect the quantum efficiency. We also study the device stability over time and identify uncorrelated discrete jumps of the pure dephasing rate at different qubit frequencies on a time scale of hours, which we attribute to independent two-level system defects in the device dielectrics, dispersively coupled to the qubit. Our single-photon source with only one input port is more compact and scalable compared to standard implementations.
Single-photon sources are of great interest because they are key elements in different promising applications of quantum technologies. Here we demonstrate a highly efficient tunable on-demand microwave single-photon source based on a transmon qubit with an intrinsic emission efficiency above $98\mathrm{%}$. The high efficiency ensures a negligible pure dephasing rate and the necessary conditions for generation of indistinguishable photons. We provide an extended discussion and analysis of the efficiency of the photon generation. To further experimentally confirm the single-photon property of the source, correlation functions of the emission field are also measured using linear detectors with a GPU-enhanced signal-processing technique. Our results experimentally demonstrate that frequency tunability and negligible pure dephasing rate can be achieved simultaneously and show that such a tunable single-photon source can be good for various practical applications in quantum communication, simulations and information processing in the microwave regime.
An on-demand single-photon source is a key element in a series of prospective quantum technologies and applications. Here we demonstrate the operation of a tuneable on-demand microwave photon source based on a fully controllable superconducting artificial atom strongly coupled to an open-ended transmission line. The atom emits a photon upon excitation by a short microwave π-pulse applied through a control line. The intrinsically limited device efficiency is estimated to be in the range 65-80% in a wide frequency range from 7.75 to 10.5 GHz continuously tuned by an external magnetic field. The actual demonstrated efficiency is also affected by the excited state preparation, which is about 90% in our experiments. The single-photon generation from the single-photon source is additionally confirmed by anti-bunching in the second-order correlation function. The source may have important applications in quantum communication, quantum information processing and sensing.
Single-photon sources of high efficiency are of great interest because they are the key elements in many prospective quantum technologies and applications. Based on our previous work, here we demonstrate a high-quality tunable microwave single-photon source based on transmon qubit with intrinsic emission efficiency more than 99%. To further confirm the single-photon property of the source, we study the single-photon interference in a Hanbury-Brown-Twiss (HBT) type setup and measure the correlation functions of the emission field using linear detectors with GPU-enhanced signal processing technique. The antibunching in second-order correlation function is clearly observed. The theoretical calculations agree well with the experimental results. Such a high-quality single-photon source may be used as a building block for quantum communication, simulation and information processing in microwave regime.
We develop a compact transmon emitter/detector (TED) superconducting circuit and demonstrate its dual functionality as a single-photon source and detector. In our setup, photons emitted by a source TED are transmitted via a meter-long coaxial cable, routed through a circulator, and captured by a measurement TED. Both TED modules operate with nominally identical parameters, highlighting the flexibility of this novel architecture. Furthermore, we introduce an efficient microwave photon detection scheme tailored to the TED. Using this setup, we detect 60% of the emitted Fock state photons and infer a 95% detection efficiency at the input of the measurement TED, which we calibrate against coherent state measurements. The reset and photon emission/detection processes each require approximately 2 μs2\,μs2μs, yielding a minimum protocol duration of 4 μs4\,μs4μs as constrained by our chosen TED parameters. Ultimately, the TED demonstrates a new use case for the recently developed double transmon coupler (DTC): a compact, drop-in, tunable, and transition-selective link between a coherent data transmon and a waveguide. Circuits like the TED will play a vital role in quantum information processing by facilitating unconditional fast reset, enabling microwave photon metrology, and serving as nascent quantum communication interfaces (QCIs). QCIs mediate entanglement distribution between quantum processing units (QPUs) within a cryostat or interface with microwave-to-optical transducers for long-range quantum networking.
Scaling up a superconducting quantum computer will likely require quantum communication between remote chips, which can be implemented using an itinerant microwave photon in a transmission line. To realize high-fidelity communication, it is essential to control the frequency and temporal shape of the microwave photon. In this work, we demonstrate the generation of frequency-tunable shaped microwave photons without resorting to any frequency-tunable circuit element. We develop a framework that treats a microwave resonator as a band-pass filter mediating the interaction between a superconducting qubit and the modes in the transmission line. This interpretation allows us to stimulate the photon emission by an off-resonant drive signal. We characterize how the frequency and temporal shape of the generated photon depends on the frequency and amplitude of the drive signal. By modulating the drive amplitude and frequency, we achieve a frequency tunability of 40 MHz while maintaining the photon mode shape time symmetric. Through measurements of the quadrature amplitudes of the emitted photons, we demonstrate a consistently high state and process fidelities around 95% across the tunable frequency range. Our hardware-efficient approach eliminates the need for additional biasing lines typically required for frequency tuning, offering a simplified architecture for scalable quantum communication.