Multiple quantum coherences experiment, simulations and applications

W. S. Warren

Najmeh Etehadi Abari, Andrey A. Rakhubovsky, Radim Filip

Abstract Quantum coherence, the ability of a system to be in a quantum superposition of pure states, is a distinct feature of quantum mechanics that has no direct analog in classical mechanics. Quantum states that possess coherence efficiently outperform their classical counterparts in fundamental science and practical applications, including quantum metrology, computation, and simulation. Generation of coherence without the need to employ strong classical drives remains a challenging and not yet experimentally explored task. Beyond individual thermally-induced coherences already proposed for different experiments, correlated quantum coherences of multiple qubits represent a new target. We prove that correlated qubit coherence emerges thermally stimulated from incoherent states in hybrid superconducting and solid-state systems comprising non-interacting qubits coupled only via Dicke-type interaction to a shared thermal mechanical oscillator, exhibits coherences beyond the Tavis–Cummings coupling and, moreover, can be advantageous in quantum sensing.

Charles P. Slichter

Serge I. Doronin, Sergey G. Vasil’ev, A. A. Samoĭlenko +2 more

Multiple quantum experiments on nuclear magnetic resonance on spins of 19 F in calcium fluorapatite have been performed. It has been shown that more than 97% of the observed signal refers to the multiple quantum coherences of the zeroth and plus/minus second orders. The dependences of the intensities of these coherences on the time of the preparation period of the multiple quantum NMR experiment have been obtained. The dipole relaxation of multiple quantum coherences on the evolution period of the multiple quantum nuclear magnetic resonance experiment has been studied. A probe providing short radio-frequency pulses with the duration up to 0.3 μs has been developed for experiments. The experimental results show that the studied system can be used for the transmission of quantum information and the study of the decoherence process in strongly correlated multispin clusters.

Chang‐shui Yu, Si‐ren Yang, Bao-qing Guo

A. Cipris, Mateus Antônio Fernandes Biscassi, J. C. C. Capella +9 more

Cold atomic clouds are promising platforms for generating correlated photons, but multiple scattering and associated Doppler broadening limit their temporal coherence. Here we demonstrate that cloud geometry provides a powerful means to extend the coherence time of scattered light. In the experiment, intensity-correlation measurements show that an elongated (quasi-1D) cloud exhibits systematically longer coherence times than a spherical (3D) cloud of the same on-axis optical thickness, as a direct consequence of the suppression of multiple scattering in the elongated geometry. Random-walk simulations reproduce this trend and further show that elongation drives the coherence time toward the single-scattering limit. The combined results establish cloud geometry as a robust control parameter for temporal coherence in cold-atom ensembles, with potential applications in quantum optics and communication.