AbstractHybrid quantum photonics combines classical photonics with quantum emitters in a postprocessing step. It facilitates to link ideal quantum light sources to optimized photonic platforms. Optical cavities enable to harness the Purcell-effect boosting the device efficiency. Here, we postprocess a free-standing, crossed-waveguide photonic crystal cavity based on Si3N4 with SiV− center in nanodiamonds. We develop a routine that optimizes the overlap with the cavity electric field utilizing atomic force microscope (AFM) nanomanipulation to attain control of spatial and dipole alignment. Temperature tuning further gives access to the spectral emitter-cavity overlap. After a few optimization cycles, we resolve the fine-structure of individual SiV− centers and achieve a Purcell enhancement of more than 4 on individual optical transitions, meaning that four out of five spontaneously emitted photons are channeled into the photonic device. Our work opens up new avenues to construct efficient quantum photonic devices.
Spin-based, quantum-photonics
promise to realize distributed quantum
computing and quantum networks. The performance depends on an efficient
entanglement distribution where cavity quantum electrodynamics could
boost the efficiency. The central challenge is the development of
compact devices with large spin-photon coupling rates and a high operation
bandwidth. Photonic crystal cavities comprise strong field confinement
but require highly accurate positioning of atomic systems in mode
field maxima. Negatively charged silicon-vacancy centers in diamond
emerged as promising atom-like systems. Spectral stability and access
to long-lived, nuclear-spin memories enabled elementary demonstrations
of quantum network nodes, including memory-enhanced quantum communication.
In a hybrid approach, we deterministically place SiV-containing nanodiamonds
inside one hole of one-dimensional, freestanding, Si3N4-based photonic crystal cavities and coherently couple individual
optical transitions to cavity modes. We optimize light–matter
coupling utilizing two-mode composition, waveguiding, Purcell-enhancement,
and cavity-resonance tuning. The resulting photon flux increases by
14 compared to free space. Corresponding lifetime-shortening below
460 ps puts potential operation bandwidth beyond GHz rates.
Coherent exchange of single photons is at the heart of applied quantum optics. The negatively-charged silicon vacancy center in diamond is among most promising sources for coherent single photons. Its large Debye–Waller factor, short lifetime and extraordinary spectral stability is unique in the field of solid-state single photon sources. However, the excitation and detection of individual centers requires high numerical aperture (NA) optics which, combined with the need for cryogenic temperatures, puts technical overhead on experimental realizations. Here, we investigate a hybrid quantum photonics platform based on silicon-vacancy center in nanodiamonds and metallic bullseye antenna to realize a coherent single-photon resource that operates efficiently down to low NA optics with an inherent resistance to misalignment.
Quantum random number generation is a key ingredient for quantum cryptography and fundamental quantum optics and could advance Monte Carlo simulations and machine learning. An established generation scheme is based on single photons impinging on a beam splitter. Here, we experimentally demonstrate quantum random number generation solely based on the symmetric emission profile of a dipole aligned orthogonal to the laboratory frame. The demonstration builds on defect centers in hexagonal boron nitride that emit photons in random directions within the dipole emission profile and benefits from the ability to manipulate and align the emission directionality. We prove the randomness in correlated photon detection events making use of the NIST randomness test suite and show that the randomness remains for two independently emitting defect centers. The scheme can be extended to random number generation by coherent single photons with potential applications in solid-state based quantum communication at room temperature.
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