Non-destructive detection of photonic qubits is an enabling technology for quantum information processing and quantum communication. For practical applications such as quantum repeaters and networks, it is desirable to implement such detection in a way that allows some form of multiplexing as well as easy integration with other components such as solid-state quantum memories. Here we propose an approach to non-destructive photonic qubit detection that promises to have all the mentioned features. Mediated by an impurity-doped crystal, a signal photon in an arbitrary time-bin qubit state modulates the phase of an intense probe pulse that is stored during the interaction. Using a thulium-doped waveguide in lithium niobate, we perform a proof-of-principle experiment with macroscopic signal pulses, demonstrating the expected cross-phase modulation as well as the ability to preserve the coherence between temporal modes. Our findings open the path to a new key component of quantum photonics based on rare-earth-ion doped crystals.
Non-destructive detection of photonic qubits is an enabling technology for quantum information processing and quantum communication. For practical applications such as quantum repeaters and networks, it is desirable to implement such detection in a way that allows some form of multiplexing as well as easy integration with other components such as solid-state quantum memories. Here we propose an approach to non-destructive photonic qubit detection that promises to have all the mentioned features. Mediated by an impurity-doped crystal, a signal photon in an arbitrary time-bin qubit state modulates the phase of an intense probe pulse that is stored during the interaction. Using a thulium-doped waveguide in lithium niobate, we perform a proof-of-principle experiment with macroscopic signal pulses, demonstrating the expected cross-phase modulation as well as the ability to preserve the coherence between temporal modes. Our findings open the path to a new key component of quantum photonics based on rare-earth-ion doped crystals.
Abstract Non-destructive detection of photonic qubits is an enabling technology for quantum information processing and quantum communication. For practical applications, such as quantum repeaters and networks, it is desirable to implement such detection in a way that allows some form of multiplexing as well as easy integration with other components such as solid-state quantum memories. Here, we propose an approach to non-destructive photonic qubit detection that promises to have all the mentioned features. Mediated by an impurity-doped crystal, a signal photon in an arbitrary time-bin qubit state modulates the phase of an intense probe pulse that is stored during the interaction. Using a thulium-doped waveguide in LiNbO3, we perform a proof-of-principle experiment with macroscopic signal pulses, demonstrating the expected cross-phase modulation as well as the ability to preserve the coherence between temporal modes. Our findings open the path to a new key component of quantum photonics based on rare-earth-ion-doped crystals.
Nondestructive detection of photonic qubits will enable important applications in photonic quantum information processing and quantum communications. Here we present an approach based on a solid-state cavity containing an ensemble of rare-earth ions. First a probe pulse containing many photons is stored in the ensemble. Then a single signal photon, which represents a time-bin qubit, imprints a phase on the ensemble that is due to the ac Stark effect. This phase does not depend on the exact timing of the signal photon, which makes the detection insensitive to the time-bin qubit state. Then the probe pulse is retrieved and its phase is detected via homodyne detection. We show that the cavity leads to a dependence of the imprinted phase on the probe photon number, which leads to a spreading of the probe phase, in contrast to the simple shift that occurs in the absence of a cavity. However, we show that this scenario still allows nondestructive detection of the signal. We discuss potential implementations of the scheme, showing that high success probability and low loss should be simultaneously achievable.
Advanced applications of quantum information science, such as long-distance quantum communication based on quantum repeaters, require photons to be interfaced with different devices. These devices, such as single photon detectors, quantum memories, quantum signal processors, and linear optical elements, may be integrated on a single chip to enable efficient, robust and scalable implementations. With aim of constructing a quantum repeater, and towards realizing integrated optical quantum memories and signal processors in general, we experimentally develop quantum light-matter interfaces using a cryogenically-cooled rare-earth-ion-doped waveguide, namely thulium-doped lithium niobate (Tm3+:LiNbO3). As the basis for our work, we describe a quantum repeater architecture that uses spectral multiplexing and quantum memories that operate with a fixed storage time. Our repeater architecture promises efficient operation, is compatible with the properties of cryogenically-cooled rare-earth-ion-doped crystals, and simplifies the demands of quantum memories compared to other architectures. To demonstrate the feasibility of our repeater design, we utilize our light-matter interface as a quantum memory to perform several experimental demonstrations. These include high-fidelity storage and retrieval of 26 spectrally-multiplexed quantum bits encoded into single-photon-level laser pulses, high-fidelity storage and retrieval of single and entangled photons derived from a photon-pair source, and high-visibility two-photon interference between weak laser pulses that are stored in one or two, separate, quantum memories. The unique properties of our light-matter interface allow us to demonstrate additional protocols that further highlight its promise for integrated quantum signal processing. By combining our Tm3+:LiNbO3 waveguide with a LiNbO3 waveguide phase modulator, we demonstrate operations such as sequencing, filtering, interference, and compression of laser pulses attenuated to the single-photon level. In another experiment, we measure the cross-phase modulation between strong pulses, by which we demonstrate photon-photon interactions that point towards non-destructive measurements of quantum bits. Since the performance of all aforementioned protocols, and future light-matter applications, hinge on the basic spectroscopic properties of our waveguide, we measure these properties at temperatures as low as 800 millikelvin. Our findings, discussed over several attached publications, usher the development of integrated quantum memories and processors for multi-component optical quantum information applications such as repeaters and networks.
Quantum light-matter interfaces that reversibly map the quantum state of photons onto the quantum states of atoms, are essential components in the quantum engineering toolbox with applications in quantum communication, computing, and quantum-enabled sensing. In this talk I present our progress towards developing on-chip quantum light-matter interfaces based on nanophotonic resonators fabricated in rare-earth-doped crystals known to exhibit the longest optical and spin coherence times in the solid state. We recently demonstrated coherent control of neodymium (Nd3+) ions coupled to yttrium orthosilicate Y2SiO5 (YSO) photonic crystal nano-beam resonator. The coupling of the Nd3+ 883 nm 4I9/2-4F3/2 transition to the nano-resonator results in a 40 fold enhancement of the transition rate (Purcell effect), and increased optical absorption (~80%) - adequate for realizing efficient optical quantum memories via cavity impedance matching. Optical coherence times T2 up to 100 μs with low spectral diffusion were measured for ions embedded in photonic crystals, which are comparable to those observed in unprocessed bulk samples. This indicates that the remarkable coherence properties of REIs are preserved during nanofabrication process. Multi-temporal mode photon storage using stimulated photon echo and atomic frequency comb (AFC) protocols were implemented in these nano-resonators. Our current technology can be readily transferred to Erbium (Er) doped YSO devices, therefore opening the possibility of efficient on-chip optical quantum memory at 1.5 μm telecom wavelength. Integration with superconducting qubits can lead to devices for reversible quantum conversion of optical photons to microwave photons.
Photonic quantum memories are important devices in quantum information science, and are crucial for several applications including quantum repeaters and quantum networks. Rare-earth (RE) doped crystals are promising candidates as quantum memories for light as they offer coherence properties comparable to those of atomic systems, but free of the drawbacks deriving from atomic motion. The research on RE based quantum memories has been so far mostly focused on the mapping of photonic quantum bits to optical collective excitations, but this leads to short lived and mostly pre-determined storage. However, some RE ions, as Praseodymium and Europium, exhibit the suitable energy level scheme, with three long-lived hyperfine ground states, to enable the spin-wave storage by transferring the collective optical excitations into collective spin excitations. Proof of principle spin-wave quantum memories have been reported in rare-earth doped crystals, using weak coherent states as input [1,2]. Here, I will present our recent results on the realization of multimode spin-wave quantum memories in a Praseodymium doped crystal, using non-classical input light. [1] M. Gündoğan, P. M. Ledingham, K. Kutluer, M. Mazzera and H. de Riedmatten , A solid state spin-wave quantum memory for time-bin qubits, Phys. Rev. Lett. 114, 230501 (2015) [2] P. Jobez, C. Laplane, N. Timoney, N. Gisin, A. Ferrier, P. Goldner, and M. Afzelius, Coherent Spin Control at the Quantum Level in an Ensemble-Based Optical Memory, Phys. Rev. Lett. 114, 230502 (2015)
Entanglement between single spins and photons is an important resource in quantum information science, e.g. in quantum networking. Rare-earth ions in dielectric crystals have emerged as a promising candidate for this task. Rare-earth ion doped solids have been used so far mostly as ensemble-based quantum memories. However, they also feature promising properties for single ion detection and manipulation, such as long-lived spins, narrow optical transitions and preservation of coherence properties when inserted in nanostructures. Because of the long lifetimes of the optical t