Spin-bearing molecules as optically addressable platforms for quantum technologies.

Efforts to harness quantum hardware relying on quantum mechanical principles have been steadily progressing. The search for novel material platforms that could spur the progress by providing new functionalities for solving the outstanding technological problems is however still active. Any physical property presenting two distinct energy states that can be found in a long-lived superposition state can serve as a quantum bit (qubit), the basic information processing unit in quantum technologies.

Anomalous Subkelvin Thermal Frequency Shifts of Ultranarrow Linewidth Solid State Emitters.

We investigate the frequency response of narrow spectral holes in a doped crystal structure as a function of temperature below 1 K. We identify a particular regime in which this response significantly deviates from the expected two-phonon Raman scattering theory. Namely, near 290 mK, we observed a behavior exhibiting a temperature-dependent frequency shift of zero to first order.

Synthesis and Crystal Structure of the Europium(II) Hydride Oxide Iodide EuHOI Showing Blue-Green Luminescence.

As the first europium(II) hydride oxide iodide, dark red single crystals of EuHOI could be synthesized from oxygen-contaminated mixtures of EuH and EuI. Its orthorhombic crystal structure ( = 1636.97(9) pm, = 1369.

Microwave Fluorescence Detection of Spin Echoes.

Counting the microwave photons emitted by an ensemble of electron spins when they relax radiatively has recently been proposed as a sensitive method for electron paramagnetic resonance spectroscopy, enabled by the development of operational single microwave photon detectors at millikelvin temperature. Here, we report the detection of spin echoes in the spin fluorescence signal. The echo manifests itself as a coherent modulation of the number of photons spontaneously emitted after a π/2_{X}-τ-π_{Y}-τ-π/2_{Φ} sequence, dependent on the relative phase Φ.

Single-electron spin resonance detection by microwave photon counting.

Electron spin resonance spectroscopy is the method of choice for characterizing paramagnetic impurities, with applications ranging from chemistry to quantum computing, but it gives access only to ensemble-averaged quantities owing to its limited signal-to-noise ratio. Single-electron spin sensitivity has, however, been reached using spin-dependent photoluminescence, transport measurements and scanning-probe techniques. These methods are system-specific or sensitive only in a small detection volume, so that practical single-spin detection remains an open challenge.