Experimental Protection of the Spin Coherence of a Molecular Qubit Exceeding a Millisecond

Molecular qubits are promising as they can benefit from tailoring and versatile design of chemistry. It is essential to reduce the decoherence of molecular qubits caused by their interactions with the environment. Herein the dynamical decoupling (DD) technique is utilized to combat such decoherence. The coherence time for a transition-metal complex (PPh_4)_2Cu(mnt)_2 is prolonged from 6.8 µs to 1.4 ms. The ratio of the coherence time and the length of \pi/2 pulse, defined as the single qubit figure of merit (Q_\rm M), reaches 1.4 \times 10^5, which is 40 times greater than what previously reported for this molecule. Our results show that molecular qubits, with milliseconds coherence time, are promising candidates for quantum information processing.