Spectral Hong–Ou–Mandel Interference between Independently Generated Single Photons for Scalable Frequency‐Domain Quantum Processing

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.

Toward quantum networking with frequency-bin qudits

“…The previous section focused on frequency-domain-based characterization of BFC states, but many of the same coherence effects can be observed in the time domain as well. Time-resolved BFC correlation functions provide insights into coherence across bins (which plays a pivotal role in entanglement 7,8 ), spectral purity within a bin (indispensable for interference between biphotons from diverse sources [26][27][28] ), and the temporal mode profile (the matching of which is crucial for interfacing photons with stationary qubits 29,30 ). In this section, we focus on time-resolved measurements of second-order coherence, 31 g (2) (τ ), for signal (or idler) photons emanating from microrings.…”

Steering of Quantum Walks through Coherent Control of High-dimensional Bi-photon Quantum Frequency Combs with Tunable State Entropies

“…The distance between the adjacent bandpass filters (BPFs) defines the free spectral range (FSR) of the QFC. The femtosecond (fs)-laser allows producing a broad single-mode frequency bandwidth for each photon with respect to CW-pumping 52,57,58 . Together with a special filter, this may result in multiple anti-diagonal lines in the JSI.…”

Controlling Frequency-Domain Hong-Ou-Mandel Interference via Electromagnetically Induced Transparency

“…Studies of frequency-domain HOM interference for single photons have relied on linear optics, which involve the use of electro-optic phase modulators [16][17][18], or the nonlinear effects of solid materials [19][20][21]. Both schemes operate under far-detuned interaction conditions and thus require high-voltage amplifiers or strong pump light; however, these methods often generate adjacent sidebands or parametric noise photons, reducing the visibility of HOM interference [22,23]. Herein, we propose another promising scheme based on near-resonant nonlinear optics that enables frequency-domain HOM interference with high visibility.…”