Quantum Memory of the Universe

Xiao Yuan, Yunchao Liu, Qi Zhao +3 more

Abstract Quantum memory—the capacity to faithfully preserve quantum coherence and correlations—is essential for quantum-enhanced technology. There is thus a pressing need for operationally meaningful means to benchmark candidate memories across diverse physical platforms. Here we introduce a universal benchmark distinguished by its relevance across multiple key operational settings, exactly quantifying (1) the memory’s robustness to noise, (2) the number of noiseless qubits needed for its synthesis, (3) its potential to speed up statistical sampling tasks, and (4) performance advantage in non-local games beyond classical limits. The measure is analytically computable for low-dimensional systems and can be efficiently bounded in the experiment without tomography. We thus illustrate quantum memory as a meaningful resource, with our benchmark reflecting both its cost of creation and what it can accomplish. We demonstrate the benchmark on the five-qubit IBM Q hardware, and apply it to witness the efficacy of error-suppression techniques and quantify non-Markovian noise. We thus present an experimentally accessible, practically meaningful, and universally relevant quantifier of a memory’s capability to preserve quantum advantage.

Ramón Alonso‐Sanz

Mikio Namiki, Y. Aizawa, Kei‐ichi Maeda +1 more

Y. D. Wang, YueYang Li, Zhigang Song +1 more

We propose a novel solid state based protocol to implement the universal quantum storage for electronic spin qubit. The quantum memory in this protocol is the magnons in the ring array of nuclei in a quantum well. We show that the quantum information carried by an arbitrary state of the electronic spin can be coherently mapped onto the magnon excitations in the spin wave quantum memory. With appropriate external control, the stored quantum state in quantum memory can be read out reversibly. We also explore the novel mechanism of quantum decoherence due to the inhomogeneous couplings between the electronic spin and the nuclear spins.

Jinghang Zhang, Yu Luo

Quantum memory plays a critical role in quantum communication, sensing, and computation. However, studies on quantum memory under a unified benchmarking framework remain scarce. In this paper, we propose a weight-based quantifier as a benchmarking method to evaluate the performance advantage of quantum memory in nonlocal exclusion tasks. We establish a general lower bound for the weight-based measure of quantum memory. Moreover, this measure provides fundamental theoretical bounds for transforming a general channel into an ideal quantum memory. Finally, we present explicit calculations of the weight-based quantifier for various channels, including unitary channels, depolarizing channels, maximal replacement channels, stochastic damping channels, and erasure channels.

N. S. Perminov, D. Yu. Tarankova, S. A. Moiseev

Abstract We propose a scheme of a universal block of broadband quantum memory consisting of three ring microresonators forming a controllable frequency comb and interacting with each other and with a common waveguide. We find the optimal parameters of the microresonators showing the possibility of highly efficient storage of light fields in this memory block and we demonstrate the procedure for gluing several memory blocks for increasing the spectral range of the composite quantum memory while maintaining high efficiency.