Optical and spin manipulation of non-Kramers rare-earth ions in a weak magnetic field for quantum memory applications

Abstract

Rare-earth ion doped crystals have proven to be solid platforms for implementing quantum memories. Their potential use for integrated photonics with large multiplexing capability and unprecedented coherence times is at the core of their attractiveness. The best performances of these ions are, however, usually obtained when subjected to a DC magnetic field, but consequences of such fields on the quantum memory protocols have only received little attention. In this paper, we focus on the effect of a DC bias magnetic field on the population manipulation of non-Kramers ions with nuclear quadrupole states, both in the spin and optical domains, by developing a simple theoretical model. We apply this model to explain experimental observations in a 151 Eu :Y 2 SiO 5 crystal, and highlight specific consequences on the atomic frequency comb spin-wave protocol. The developed analysis should allows predicting optimal magnetic field configurations for various protocols.

Storage of photonic time-bin qubits for up to 20 ms in a rare-earth doped crystal

“…These two observations might be a sign of the presence of beats originating in the different phase paths available to the atoms during storage, due to the small Zeeman splitting of the ground state doublets in this regime of weak magnetic field. Similar effects have been shown in a more detailed model of interaction between a system with splittings smaller than the RF pulses chirp 27 .…”

“…The η 0 efficiency is consistent with the initial optical depth of 6 in our double-pass input configuration (each pass provides an optical depth of about 3). The data also shows a modulation of the efficiency dependent on the external magnetic field, which is an effect of the Zeeman splitting onto the AFC preparation process 27 . Whenever the comb periodicity is a multiple of the excited state splitting, the optical depth of the prepared AFC is reduced.…”

“…At zero magnetic field, the protocol enabled to achieve storage of multiple coherent single photon-level pulses up to about 1 ms 23 . However, it has been shown that even a weak magnetic field can increase the coherence lifetime 22,[33][34][35] , which motivated us to use a ∼ 1.35 mT field along the D 1 axis 27 .…”

“…A particular challenge of long duration quantum storage in RE systems is noise introduced by the application of the dynamical decoupling (DD) sequences that are required to overcome the inhomogeneous spin dephasing 23 and the spectral diffusion 20,22 . To reduce the noise one can apply error-compensating DD sequences 25 , or increase the spin coherence time by applying magnetic fields to reduce the required number of pulses 20,26,27 .…”

A readout-integrated time-bin qutrit analyzer for echo-based quantum memories

“…After being mapped to the spin transition, the coherence is stored there for 20 ms. To preserve coherence, we perform a single XY4 decoupling sequence [44]. Additionally, during the whole experiment we apply a static magnetic field of 1.35 mT along the D 1 -axis of the crystal which has been shown to increase the coherence time of the spin transition significantly [16,45]. A more detailed description of this setup and a characterization of its performance as a memory platform can be found in Ref.…”