Entanglement preserving memory for quantum microwaves

Christopher J. Axline, Luke Burkhart, Wolfgang Pfaff +9 more

Alkim Bozkurt, Omid Golami, Yue Yu +2 more

Kirill Viktorovich Petrovnin, Nikolay Sergeevich Perminov, Oleg N. Sherstyukov +1 more

We consider a protocol of broadband quantum memory on a controlled frequency comb of spectral lines of ring microwave resonators connected to a common strip waveguide. A prototype of this memory is manufactured, on which the room-temperature preservation of microwave pulses with an efficiency of about 3 % is demonstrated. The experimentally obtained efficiency can be enhanced to a level above 90 % using modern microwave technologies and conducting experiments at helium temperatures, which opens a new way for the development of integrated microwave quantum memory.

A. Asghari Nejad, Hassan Randjbar Askari

Aleksei R. Matanin, Nikita S. Smirnov, Аnton I. Ivanov +8 more

Microwave quantum memory represents a critical component for quantum radars and resource-efficient approaches to quantum error correction. Superconducting microwave resonators provide highly efficient storage, long coherence times, on-demand reading, and even memory pulse engineering, but it is still challenging to overcome design and materials induced loss channels for on-chip realization. In this Letter, we present a novel architecture of integrated superconducting quantum memory with a dynamically controlled RF-SQUID coupling element in pulse regime, thus ensuring high efficiency storage and cycling storage time. It demonstrates a memory cycle time of 1.51 μs and 57.5(4)% storage fidelity with preservation of the stored pulse shape during the retrieval at single-photon level excitations. We establish that while the proposed active coupler realization introduces no measurable fidelity degradation, the primary limitation arises from impedance matching and materials imperfections. Still the device was used only for storing finite-duration near-single-photon classical microwave pulses, we assert that it operates as a linear device when the photon population in the common resonator remains low so it should be compatible with quantum state storage. The proposed architecture highlights a disruptive potential for on-chip qubit and memory integration for scalable quantum error correction, while identifying specific avenues for near-unity storage fidelity.

K. S. Tikhonov, T. Yu. Golubeva, Yu. M. Golubev

The possibility of preserving an entangled state of two signal pulses during writing and retrieval processes in a multimode quantum memory is investigated. Two stationary laser sources of light squeezed in two orthogonal quadratures are used for generation of the entangled state. “Carved out” pulses of appropriate duration are mixed on a symmetric beamsplitter, which allows obtaining the desired entanglement. It is assumed that each of the obtained entangled pulses is stored in a separate memory cell and subsequently retrieved from it. The obtained analytical expressions for Duan entanglement criterion are analyzed numerically for the case of broadband memory. It is demonstrated that the entanglement of pulses can be effectively preserved not only in the case of symmetric geometry of the experiment, wherein both pulses are written in two identical independent memory cells, but also in the case of different memory cells and even when one of the cells is absent completely. An important distinguishing feature of the problem under consideration, compared to the single mode case where high memory efficiency ensures good preservation of quantum properties of light, is the possibility of obtaining good preservation of entanglement at low memory efficiency (under shortened readout times).