Stark echo modulation for quantum memories

Abstract

Quantum memories for optical and microwave photons provide key functionalities in quantum processing and communications. Here we propose a protocol well adapted to solid state ensemble based memories coupled to cavities. It is called Stark Echo Modulation Memory (SEMM), and allows large storage bandwidths and low noise. This is achieved in a echo like sequence combined with phase shifts induced by small electric fields through the linear Stark effect. We investigated the protocol for rare earth nuclear spins and found a high suppression of unwanted collective emissions that is compatible with single photon level operation. Broadband storage together with high fidelity for the Stark retrieval process is also demonstrated. SEMM could be used to store optical or microwave photons in ions and/or spins. This includes NV centers in diamond and rare earth doped crystals, which are among the most promising solid-state quantum memories.PACS numbers: 03.67. Lx,76.30.Kg,76.60.Lz Quantum memories (QM) are essential components in quantum information processing. They enable storage and on-demand retrieval of quantum states and allow using fast but short-lived processing qubits, or photonic states that are excellent carriers of quantum information but are difficult to store. QM for light find applications in linear optics quantum computing, as well as in quantum communications and networks, where they could enable distribution of entangled states over long distances using quantum repeater architectures [1,2]. There is also a growing interest in spin based quantum memories that store micro-wave photons which in turn can be interfaced to superconducting qubits [3]. In the solid state, optical and microwave QM based on inhomogeneously broadened ensemble are actively investigated in rare earth (RE) ion doped crystals and diamonds containing NV centers [4-9] These two systems are well adapted to highly multimode storage, where multiple photons with large bandwidths are stored for long times [10]. Moreover, high efficiency can be obtained by coupling these centers to a cavity, overcoming their weak interactions with photons, either for spin or optical transitions [11][12][13]. A natural protocol to implement QM in inhomogeneous ensembles is the spin or photon echo [14,15] which recovers the initial excitation of the system by applying a π pulse to the storage transition. This inverts the atomic or spin phase evolution and results in a collective emission, the so-called echo. However, this scheme does not allow low-noise operation, a key parameter for quantum memories, which must store photonic qubits like single photons [16]. This is because the collective emission occurs in an inverted medium which produces a too large spontaneous emission at the memory output. To avoid this situation, several protocols have been proposed and experimentally investigated. However, they require spectral tailoring [17][18][19][20][21], which requires a long lived storage level and can reduce bandwidth, or particular spatial phase matching conditions...

High-resolution optical spectroscopy and magnetic properties ofYb3+inY2SiO5Welinski1, Ferrier2, Afzelius3 et al. 2016Phys. Rev. B404391View full textAdd to dashboardCite

“…This can be used to interface microwave photons to a RE doped crystal through a superconducting resonator 22,23 and obtain quantum memories for superconducting qubits. [24][25][26] In this case too, nuclear hyperfine transitions can provide long storage time. We recently showed that 145 Nd 3+ :Y 2 SiO 5 hyperfine transitions have ground state coherence lifetimes up to 9 ms at 5 K, whereas the electron spin T 2 is about 100 µs.…”

A controlled ac Stark echo for quantum memories

“…Recently demonstrated ac Stark modulations in a double rephasing photon echo scheme 23 have exhibited a similar mechanism of atom phase control to dc Stark echoes 12 , 13 , in which the Stark field provides an on-purpose phase shift (turbulence) so that the transient atoms cannot be concurrently rephased for the first echo. As mentioned above, however, ref.…”

“…To overcome the population inversion constraint in photon echoes, several modified photon echo schemes have been developed for quantum memory applications since 2001 1 . The modified photon echo schemes for quantum memory protocols include controlled reversible inhomogeneous broadening (CRIB) 1 – 5 and atomic frequency comb (AFC) echoes 6 – 9 for a single rephasing scheme, and silent echoes 10 , 11 , dc Stark echoes 12 , 13 , controlled double rephasing (CDR) echoes 14 , 15 and optically locked photon echoes 16 for a double rephaisng scheme. These modified photon echo protocols can also be categorized as two-level 3 , 4 , 6 , 9 – 13 or three-level 1 , 2 , 5 , 7 , 8 , 14 – 16 schemes.…”

“…In that scheme, the backward rephasing pulse may not fully rephase the data-excited coherence due to the Beer’s law-governed opposite absorption profile. The second idea is to use dc Stark effects with spectral tailoring 12 , 13 . Here, we present a new quantum memory protocol of controlled ac Stark echoes (CASE) based on CDR, where unbalanced ac Stark fields work to silence the first echo so that it does not affect the second echo.…”

Recent Advances in Rare Earth Doped Inorganic Crystalline Materials for Quantum Information Processing

“…Nevertheless, they can be useful to manipulate spin state because their effect can accumulate over long coherence lifetimes. This has been used to design a low noise and broadband quantum memory protocol that can be used for optical, electron and nuclear spin transitions …”