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Advanced Physics Research

Experimental Demonstration of Radio‐Frequency Hong‐Ou‐Mandel Interference With Emulated Single‐Photon States

Andrey Sheleg, Dmytro Vovchuk, K. Boiko, Pavel Ginzburg, G. Slepyan, Amir Boag, Alexander B. Mikhalychev, Alexander P. Ulyanenkov, Toms Salgals, Dmitri S. Mogilevtsev

Published Apr 22, 2026• 0 citations
Publisher

Abstract

ABSTRACT We report an experimental demonstration of room‐temperature Hong–Ou–Mandel (HOM) interference at a radio‐wave frequency of 120 MHz using single‐photon states built from phase‐averaged coherent states by the emulation procedure proposed in the recent work. This emulation approach enables observation of quantum effects in spectral regimes where conventional single‐photon sources and detectors are unavailable or require cryogenic conditions. By constructing a high‐fidelity approximation of a single‐photon state with phase‐averaged coherent states, we observe the normalized second‐order intensity correlation dips significantly below the classical limit of 0.5. The method allows for tunable noise suppression via optimization of the state representation. Our results establish the feasibility of using conditionally prepared classical states to simulate quantum interference phenomena in the radio‐frequency domain.

DOI
10.1002/apxr.202500204

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arXiv:2506.03098•Advanced Quantum Technologies•Nov 28, 2025•1 citation
ABSTRACT We report an experimental demonstration of room‐temperature Hong–Ou–Mandel (HOM) interference at a radio‐wave frequency of 120 MHz using single‐photon states built from phase‐averaged coherent states by the emulation procedure proposed in the recent work. This emulation approach enables observation of quantum effects in spectral regimes where conventional single‐photon sources and detectors are unavailable or require cryogenic conditions. By constructing a high‐fidelity approximation of a single‐photon state with phase‐averaged coherent states, we observe the normalized second‐order intensity correlation dips significantly below the classical limit of 0.5. The method allows for tunable noise suppression via optimization of the state representation. Our results establish the feasibility of using conditionally prepared classical states to simulate quantum interference phenomena in the radio‐frequency domain.
We report an experimental demonstration of room-temperature Hong-Ou-Mandel (HOM) interference at a radio-wave frequency of 120 MHz using conditional build-up of quantum states from classical phase-averaged coherent states. This approach enables observation of quantum effects in spectral regimes where conventional single-photon sources and detectors are unavailable or require cryogenic conditions. By constructing a high-fidelity approximation of a single-photon state with phase-averaged coherent states, we observe the normalized second-order intensity correlation dips significantly below the classical limit of 0.5. The method allows for tunable noise suppression via optimization of the state representation. Our results establish the feasibility of using conditionally prepared classical states to simulate quantum interference phenomena in the radio-frequency domain. This technique opens the door to realizing other quantum protocols, such as Bell inequality tests, in frequency ranges where standard quantum technologies are currently infeasible.
Abstract The photon's frequency degree of freedom, being compatible with mature telecom infrastructure, offers large potential for the stable and controllable realization of photonic quantum processing applications such as the quantum internet. The Hong–Ou–Mandel effect, as a two‐photon interference phenomenon, serves as a central building block for such frameworks. A key element yet missing to enable meaningful frequency‐based implementations as well as scalability in the number of processed photons, is the demonstration of the Hong–Ou–Mandel effect between independently created photons of different frequencies. The experimental implementation of bosonic and fermionic frequency domain Hong–Ou–Mandel interference between independently generated single photons is reported here, with measured visibilities of 74.31% ± 3.56% and 86.44% ± 8.27%, respectively. This is achieved through a scalable photonic frequency circuit that creates two post‐selected pure single photons, which undergo frequency mixing at an electro‐optic phase modulator. The system is on‐the‐fly reconfigurable allowing to probe bosonic and fermionic Hong–Ou–Mandel interference in the same experimental setup. The work demonstrates the versatility of frequency domain processing and its scalability toward higher photon numbers, which enables new quantum gate concepts as well as the establishment of frequency‐based large‐scale quantum networks.
Recently a single-photon frequency converter by a nonlinear optical medium with a strong pump light [1] has been actively studied for quantum information processing [2]. The effective Hamiltonian of the process is described as a frequency-domain beamsplitter, which has two different frequency modes in its input and output. The transmittance is tunable by a pump power for the nonlinear optical effect. Such a frequency-domain beamsplitter is expected to cause an interference of two photons of different colors [3] in the context of a Hong–Ou–Mandel (HOM) experiment. In this study, we first observed the HOM dip in an optical range by using a frequency-domain beamsplitter.
The frequency degree-of-freedom, being compatible with well-developed omnipresent optical telecommunication infrastructure, allows for stable, controllable and scalable encoding of quantum information [1] . The HOM effect between independent photons, as a central building block to, e.g., quantum key distribution (QKD), quantum teleportation and entanglement swapping, has been mainly employed within the spatial domain [2] . A key element yet missing to enable scalable and thus real-world frequency-based implementation of quantum computation and non-classical communication, is the demonstration of Hong-Ou-Mandel (HOM) interference between independently created photons of different frequencies. To date, spectral bosonic HOM interference between single photons, produced out of the same continuous-wave (cw)-excited spontaneous parametric down conversion (SPDC) process has been demonstrated [3] , which however does not allow scalability due to the spectral impurity inherent to the proposed approach.
In the context of Fock states, demonstrating multiphoton quantum interference, e.g., the generalized Hong-Ou-Mandel (HOM) interference, is at the core of many applications of quantum technologies. However, it is difficult to demonstrate high-visibility quantum interference for a large number of photons. Here, we introduce an experimentally feasible proposal to achieve this goal using phase-randomized weak coherent states and practical photon-number-resolving detectors. Our method can be used to obtain analytically tight bounds of the generalized HOM dip in a beam splitter, and it is robust against practical errors. The simulation shows that for an ideal detector that can resolve any number of photons without an upper bound, the proposed method can bound the generalize HOM interference for a large number of photons, e.g., 100 photons; for a practical detector that can resolve up to 29 photons, the proposed method can bound the generalized HOM interference for 56 photons with visibility 99.499.4%99.4. Our proposal is a general approach for multiphoton quantum interference in optical networks with multiple inputs and outputs.
ABSTRACT We demonstrate a scheme for high‐precision measurements of time delay based on frequency‐resolved Hong‐Ou‐Mandel (HOM) interference. Our approach is applied to weak coherent states and exploits an array of single‐photon avalanche diodes (SPADs). Unlike conventional HOM experiments, our setup enables high‐precision measurements, producing an uncertainty per coincidence of about ps even for photons separated by delays up to ps so much greater than their coherence time, where ordinary non‐resolved HOM fails. This result confirms our newly developed theoretical predictions that consider, differently from previous theoretical results, a finite frequency resolution in the detection. We compare the performance of this scheme against the conventional non‐resolved case. Experimental data align well with the predictions of quantum estimation theory, demonstrating a significant reduction in the uncertainty. Due to the physics of the frequency‐resolved HOM effect, the gain in precision is particularly high when the estimated time delay is much longer than the coherence time.