arXiv subjects

Fabian Salamon

Publications and source records attributed to Fabian Salamon.

3 recordsLinked to original sources

arXiv2026

Cavity-enhanced optical readout and control of nuclear spin qubits

Their exceptional coherence makes nuclear spins in solids a prime candidate for quantum memories in quantum networks and repeaters. Still, the direct all-optical initialization, coherent control, and readout of individual nuclear spin qubits have been an outstanding challenge. Here, this is achieved by embedding 167-Er dopants in yttrium orthosilicate in a cryogenic Fabry-Perot cavity, whose linewidth of 65 MHz is much smaller than the 0.9 GHz separation of neighboring hyperfine levels. Frequency-selective emission enhancement thus enables a single-shot readout fidelity of 91(2)%. Furthermore, a large magnetic field freezes paramagnetic impurities, leading to coherence times exceeding 0.2 s. The combination of nuclear-spin qubits with frequency-multiplexed addressing and lifetime-limited photon emission in the minimal-loss telecommunications C-band establishes 167-Er as a leading platform for long-range, fiber-based quantum networks.

quant-ph↗

arXiv2026

Spectral stability of cavity-enhanced single-photon emitters in silicon

The unrivaled maturity of its nanofabrication makes silicon a promising hardware platform for quantum information processing. To this end, efficient single-photon sources and spin-photon interfaces have been implemented by integrating color centers or erbium dopants into nanophotonic resonators. However, the optical emission frequencies in this approach are subject to temporal fluctuations on both long and short timescales, which hinders the development of quantum applications. Here, we investigate this limitation and demonstrate that it can be alleviated by integrating the emitters into Fabry-Perot instead of nanophotonic resonators. Their larger optical mode volume enables both increasing the distance to crystal surfaces and operating at a lower dopant concentration, which reduces implantation-induced crystal damage and interactions between emitters. As a result, we observe a fivefold reduction of the spectral diffusion linewidth down to 4.0(2) MHz. Calculations and experimental investigations of isotopically purified 28-Si crystals suggest that the remaining spectral instability is caused by laser-induced electric-field fluctuations. In direct comparison with a nanophotonic device, the instability is significantly reduced at the same intracavity power, enabling a tenfold increase of the optical coherence time up to 20(1) microseconds. These findings represent a key step towards spectrally stable spin-photon interfaces in silicon and their potential applications in quantum networking and distributed quantum information processing.

quant-ph↗

arXiv2024

Spectral Multiplexing of Rare-earth Emitters in a Co-doped Crystalline Membrane

The spectral addressing of many individual rare-earth dopants in optical resonators offers great potential for realizing distributed quantum information processors. To this end, it is required to understand and control the spectral properties of the emitters in micron-scale devices. Here, erbium emitters are investigated in a Fabry-Perot resonator which contains a ten-micrometer-thin membrane of crystalline yttrium orthosilicate that is co-doped with europium. The co-doping allows for tailoring the inhomogeneous distribution of the emitter frequency, which enables high-fidelity spectral multiplexing of more than 360 qubits with Purcell factors exceeding 35. At the same time, the optical coherence is preserved up to 0.62(3) ms under dynamical decoupling. Without decoupling, the coherence still reaches the lifetime limit for the emitters with the strongest Purcell enhancement that leads up to a 110-fold lifetime reduction, down to 0.104(9) ms. Future work may combine this with long-lived nuclear spin memories, which makes the investigated co-doped membranes a promising platform for quantum repeaters and distributed quantum computers.

quant-ph↗