A single molecule links microwave spin control with optical readout
Researchers used a single organic molecule in a host crystal to connect a spin qubit with light. The peer-reviewed experiment combined optical preparation and readout with microwave control at 4.5 kelvin. Protective pulse sequences extended spin coherence to about 2.2 milliseconds. The result establishes an individually addressable molecular interface component, with brightness and operating temperature among the remaining engineering constraints.
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A crystal hosts an individually addressable molecular qubit
A single organic molecule has combined optical preparation and readout with microwave control of a spin qubit in a peer-reviewed laboratory experiment. Researchers from NVision Quantum Technologies, a quantum-technology company, Ulm University and the Hebrew University of Jerusalem used a carbene held in a structurally matched ketone host crystal. Spin is intrinsic angular momentum; a qubit is a basic unit of quantum information. Light activates the molecule, prepares its spin state and reads the response, while microwaves manipulate the spin. Photon-correlation measurements were consistent with an individual emitter. The experiment operated at 4.5 kelvin, and its results apply to that molecule–host combination under cryogenic conditions.[1], [2]
Protective pulses extend coherence into milliseconds
Dynamical-decoupling pulses, which reduce the effects of environmental disturbances, extended spin coherence to about 2.2 milliseconds. Spin relaxation took 21 milliseconds. Those quantities describe different aspects of the spin's persistence. Optical measurements also examined how consistently the same molecule could be addressed: one molecule had a linewidth of 38 megahertz, while line positions remained stable over more than an hour. Such stability matters when linking a spin state with a reproducible optical signal. Chemically tailored molecules offer precise control over atomic structure, but combining readable optical transitions and long-lived spin states remains demanding. The protective pulse sequence achieved a longer coherence time than a simple echo measurement in the same platform.[1], [2]
Optical efficiency remains part of the interface design
The total quantum yield was about 10.8%, and two prominent optical lines carried around 19% of the emission. These figures describe different stages of light production and are distinct from the measured spin lifetimes. The estimated combined emission efficiency into the zero-phonon line was about 2.1%; that optical component involves no change in vibrational excitation. Brightness, quantum yield and operating temperature remain areas for improvement. The demonstrated optical interface uses the electron spin, while nuclear spins in the molecule are intended as longer-lived memories requiring further work. The experiment established a component for single-emitter quantum optics without demonstrating entanglement between distant molecules or an operating quantum network. Its chemical flexibility provides a way to investigate improved coupling and compatible host environments. The measured optical linewidth also exceeded the natural linewidth.[1], [2]
