Freezing impurities extends spin qubit coherence to 0.2 seconds

Researchers at the Max-Planck-Institut für Quantenoptik have extended the coherence of nuclear spin qubits to exceed 0.2 seconds, a duration that significantly advances the feasibility of practical quantum memory. The team achieved this milestone by embedding erbium dopants within yttrium orthosilicate and utilizing a cryogenic Fabry-Perot cavity with a linewidth of 65 MHz, smaller than the 0.9 GHz separation of hyperfine levels, to enable frequency-selective enhancement. This combination of nuclear-spin qubits, frequency-selective addressing, and photon emission in the minimal-loss telecommunications C-band positions erbium as a leading candidate for long-range, fiber-based quantum networks. A coherence time exceeding 0.2 seconds has been demonstrated in nuclear spin qubits embedded within yttrium orthosilicate, expanding the potential for practical quantum memory and long-distance quantum communication. Researchers at the Max-Planck-Institut für Quantenoptik achieved this milestone by carefully controlling the environment of erbium-167 dopants,…