Conditional Detection of Pure Quantum States of Light after Storage in a Tm-Doped Waveguide

Abstract

Conditional detection is an important tool to extract weak signals from a noisy background and is closely linked to heralding, which is an essential component of protocols for long distance quantum communication and distributed quantum information processing in quantum networks. Here we demonstrate the conditional detection of time-bin qubits after storage in and retrieval from a photon-echo based waveguide quantum memory. Each qubit is encoded into one member of a photon-pair produced via spontaneous parametric down conversion, and the conditioning is achieved by the detection of the other member of the pair. Performing projection measurements with the stored and retrieved photons onto different bases we obtain an average storage fidelity of 0.885 ± 0.020, which exceeds the relevant classical bounds and shows the suitability of our integrated light-matter interface for future applications of quantum information processing.PACS numbers: 03.67. Hk, 42.50.Ex, 32.80.Qk, 78.47.jf Quantum memories are key elements for future applications of quantum information science such as long-distance quantum communication via quantum repeaters [1, 2] and, more generally, distributed quantum information processing in quantum networks [3]. They enable reversible mapping of arbitrary quantum states between travelling and stationary carriers (i.e. light and matter). This reduces the impact of loss on the time required to establish entanglement between distant locations [1], and allows the implementation of local quantum computers based on linear optics [4]. However, towards these ends, the successful transfer of a quantum state into the memory must be announced by a heralding signal. When using an individual absorber, such a signal can be derived through the detection of a change of atomic level population [5]. In atomic ensembles, this approach is infeasible. Instead, storage is derived from the detection of a second photon that either indicates the absorption [6], or the presence of the first at the input of the memory [7] (the first approach relies on spontaneous Raman scattering, the second on using pairs of photons). Furthermore, quantum memories must allow on-demand read-out after second-long storage with high efficiency [7,8], and, for viable quantum technology, should be robust and simple to operate (e.g. be based on integrated optics).A lot of progress towards these (and other) figures of merit has been reported over the past few years, including work that explores electromagnetically induced transparency (EIT), as well as photon-echo and cavity QEDbased approaches (see [2,5,[7][8][9][10][11][12][13][14] for reviews and latest achievements). Yet, strictly, most of these experiments did not report true heralding -either heralding was not actually implemented, or the 'heralding' signal was generated only after the stored photon left the memory, or the signal could, due to technical issues, only be derived once the stored photon was detected. Nevertheless, experiments that employ photon pairs [11][12][13]15] do gain from c...

Diffusion Properties of Tm3+ in Congruent LiNbO3 Crystal

“…The analysis was accomplished by a time-of-flight second ion mass spectrometry (ION-TOF TOF SIMS V). A Cs + beam (~45 lm in diameter) of 22-32 nA at 3 keV was used to sputter a crater of 120 9 120 lm 2 and a pulsed bismuth ion beam of 1 pA at 25 keV was used to analyze the secondary ions 7 Li, 93 Nb, 16 O, and 169 Tm as a function of time. Positive secondary ions were detected.…”

“…Third, as a memory medium, a Tm 3+ -doped Ti:LN waveguide can find its use in the field of quantum communication. [15][16][17] In addition, a slightly Tm 3+ -doped (0.05 mol%) LN can be also used for data storage based on the nonvolatile two-color holography. 18 All of these interesting features or potential applications, together with the excellent electro-optic, acousto-optic, and nonlinear optical properties of LN crystal itself, show that the Tm 3+ -doped LN is also a promising host material.…”

“…[24][25][26][27] As an alternative, the Tm 3+ ions can be incorporated by diffusion-doping method. 12,[15][16][17] The merit of this method is that for the monolithic integration of active (optically pumped, rareearth-doped) and passive (unpumped) devices on a same substrate, selective rare-earth doping can avoid reabsorption in unpumped rare-earth-doped waveguide. This is the case for a three-level rare-earth ion (like Er 3+ )-doped LN waveguide device.…”

Single-photon-level optical storage in a solid-state spin-wave memory

“…This has provided a strong motivation for developing quantum memories using such systems. Following the first storage experiment at the single-photon level [19], a succession of experiments demonstrated storage of single photons [20,21] and generation of light-matter [15,16] and matter-matter entanglement using crystals [22]. The quantum memory performances have also been strongly developed, particularly in terms of storage efficiency [23,24], multimode capacity [25,26], and polarization qubit storage [21,27,28].…”

Quantum Storage of Heralded Single Photons in a Praseodymium-Doped Crystal

“…This has recently been extended to the ground state, in the regime of a few photons per pulse [29]. The storage of non-classical light generated by spontaneous parametric down-conversion (SPDC) has also been demonstrated and enabled entanglement between one photon and one collective optical atomic excitation in a crystal [30,31], entanglement between two crystals [32], and single photon qubit storage [33,34]. However, the mapping of nonclassical light using AFC in rare earth doped crystals was obtained so far only in systems with two ground state levels, thus inherently limited to the optical coherence and not directly extendable to spin-wave storage.…”