We propose a hybrid quantum computing scheme where qubit degrees of freedom for computation are combined with quantum continuous variables for communication. In particular, universal two-qubit gates can be implemented deterministically through qubit-qubit communication, mediated by a continuous-variable bus mode ("qubus"), without direct interaction between the qubits and without any measurement of the qubus. The key ingredients are controlled rotations of the qubus and unconditional qubus displacements. The controlled rotations are realizable through typical atom-light interactions in quantum optics. For such interactions, our scheme is universal and works in any regime, including the limits of weak and strong nonlinearities.
We propose a scheme to realize deterministic quantum teleportation using linear optics and hybrid qubits. It enables one to efficiently perform teleportation and universal linear-optical gate operations in a simple and near-deterministic manner using all-optical hybrid entanglement as off-line resources. Our analysis shows that our new approach can outperforms major previous ones when considering both the resource requirements and fault tolerance limits.
We investigate the performance of quantum teleportation under a lossy environment using two different types of optical hybrid qubits. One is the hybrid of the vacuum and single-photon states with coherent states and the other is the hybrid of polarized single-photon states with coherent states. We have shown that the hybrid qubit using vacuum and single-photon states is generally more robust to photon loss effects compared to the one using the photon polarization with respect to fidelities and success probabilities of quantum teleportation.
We derive the general structure of noiseless subsystems for optical radiation contained in a sequence of pulses undergoing collective depolarization in an optical fiber. This result is used to identify optimal ways to implement quantum communication over a collectively depolarizing channel, which in general combine various degrees of freedom, such as polarization and phase, into joint hybrid schemes for protecting quantum coherence.
This article reviews recent hybrid approaches to optical quantum information processing, in which both discrete and continuous degrees of freedom are exploited. There are well-known limitations to optical single-photon-based qubit and multi-photon-based qumode implementations of quantum communication and quantum computation, when the toolbox is restricted to the most practical set of linear operations and resources such as linear optics and Gaussian operations and states. The recent hybrid approaches aim at pushing the feasibility, the efficiencies, and the fidelities of the linear schemes to …
We propose a feasible scheme to realize the optical entanglement of single-photon-added coherent state (SPACS) and show that, besides the Sanders entangled coherent state, the entangled SPACS also leads to new forms of hybrid entanglement of quantum Fock state and classical coherent state. We probe the essential difference of two types of hybrid entangled state (HES). This HES provides a novel link between the discrete- and the continuous-variable entanglement in a natural way.
We propose a scheme of loss-resilient entanglement swapping between two distant parties via an imperfect optical channel. In this scheme, two copies of hybrid entangled states are prepared and the continuous-variable parts propagate through lossy media. In order to perform successful entanglement swapping, several different measurement schemes are considered for the continuousvariable parts such as single-photon detection for ideal cases and a homodyne detection for practical cases. We find that the entanglement swapping using hybrid states with small amplitudes offers larger entanglement than…
We review and compare Bell-state measurement and quantum teleportation schemes using linear optics with three different types of resources, i.e., two-photon pairs, entangled coherent states and hybrid entangled states. Remarkably, perfect teleportation with linear optics is possible in principle based on a hybrid approach that combines two-photon pairs and entangled coherent states. It turns out that hybrid approach allows to perform Bell-state measurement and local Pauli operations in a deterministic way, while it requires photon number resolving measurements.
The generation and manipulation of hybrid entanglement of light involving discrete- and continuous-variable states have recently appeared as essential resources towards the realization of heterogeneous quantum networks. Here we investigate a scheme for the remote generation of hybrid entanglement between particle-like and wave-like optical qubits based on a non-local heralding photon detection. We also extend this scheme with additional local or non-local detections. An additional local heralding allows the resulting state to exhibit a higher fidelity with the targeted entangled qubits while a…
Decoherence for a one-dimensional coupled-resonator waveguide with a two-level system inside one of resonators, induced by their interaction with corresponding environments, is investigated. Each environment is modeled as a continuum of harmonic oscillators. By finding the eigenstates of the hybrid system, which is the dressed state of the hybrid system, we calculate the lifetime of one excitation, which characterizes the existence of quantum coherence in such hybrid system and the basic quantum nature.
Historically, two complementary approaches to optical quantum information processing have been pursued: qubits and continuous-variables, each exploiting either particle or wave nature of light. However, both approaches have pros and cons. In recent years, there has been a significant progress in combining both approaches with a view to realizing hybrid protocols that overcome the current limitations. In this chapter, we first review the development of the two approaches with a special focus on quantum teleportation and its applications. We then introduce our recent research progress in realizi…
We investigate the optical response of a hybrid electro-optomechanical system interacting with a qubit. In our experimentally feasible system, tunable all-optical-switching, double-optomechanically induced transparency (OMIT) and optomechanically induced absorption (OMIA) can be realized. The proposed system is also shown to generate anomalous dispersion. Based on our theoretical results, we provide a tunable switch between OMIT and OMIA of the probe field by manipulating the relevant system parameters. Also, the normal-mode-splitting (NMS) effect induced by the interactions between the subsys…
We propose to realize the two-mode continuous-variable entanglement of microwave photons in an electro-optic system, consisting of two superconducting microwave resonators and one or two optical cavities filled with certain electro-optic medium. The cascaded and parallel schemes realize such entanglement via coherent control on the dynamics of the system, while the dissipative dynamical scheme utilizes the reservoir-engineering approach and exploits the optical dissipation as a useful resource. We show that, for all the schemes, the amount of entanglement is determined by the ratio of the effe…
Quantum information processing with hybrid protocols making use of discrete- and continuous-variable currently attracts of great interest because of its promising applications in scalable quantum computer and distant quantum network. By inducing a giant cross-Kerr nonlinearity between two cavities, we propose a general protocol for hybrid quantum gate and quantum entanglement with high fidelity between a stationary, discrete photonic qubit and a flying photonic state. Interestingly, our protocol can be used to conduct a controlled-Z quantum gate between a stationary microwave photon stored in …
We investigate the effects of atomic collisions as well as optomechanical mirror-field coupling on the optical bistability in a hybrid system consisting of a Bose-Einstein condensate inside a driven optical cavity with a moving end mirror. It is shown that the bistability of the system can be controlled by the s-wave scattering frequency which can provide the possibility of realizing a controllable optical switch. On the other hand, by studying the effect of the Bogoliubov mode, as a secondary mechanical mode relative to the mirror vibrations, on the cooling process as well as the bipartite mi…
We theoretically describe the quantum properties of a large Fresnel number degenerate optical parametric oscillator with spherical mirrors that is pumped by a Gaussian beam. The resonator is tuned so that the resonance frequency of a given transverse mode family coincides with the down-converted frequency. After demonstrating that only the lower orbital angular momentum (OAM) Laguerre-Gauss modes are amplified above threshold, we focus on the quantum properties of the rest of (classically empty) modes. We find that combinations of opposite OAM (Hybrid Laguerre-Gauss modes) can exhibit arbitrar…
Entangled photon pair sources based on bulk optics are approaching optimal design and implementation, with high state fidelities, spectral purities and heralding efficiencies, but generally low brightness. Integrated entanglement sources, while providing higher brightness and low-power operation, often sacrifice performance in output state quality and coupling efficiency. Here we present a polarization-entangled pair source based on a hybrid approach of waveguiding and bulk optics, addressing every metric simultaneously. We show 96% fidelity to the singlet state, 82% Hong-Ou-Mandel interferenc…
A tapered optical nanofiber simultaneously used to trap and optically interface of cold atoms through evanescent fields constitutes a new and well controllable hybrid quantum system. The atoms are trapped in two parallel 1D optical lattices generated by suitable far blue and red detuned evanescent field modes very close to opposite sides of the nanofiber surface. Collective electronic excitations (excitons) of each of the optical lattices are resonantly coupled to the second lattice forming symmetric and antisymmetric common excitons. In contrast to the inverse cube dependence of the individua…
The wave-particle duality of light has led to two different encodings for optical quantum information processing. Several approaches have emerged based either on particle-like discrete-variable states, e.g. finite-dimensional quantum systems, or on wave-like continuous-variable states, e.g. infinite-dimensional systems. Here, we demonstrate the first measurement-induced generation of entanglement between optical qubits of these different types, located at distant places and connected by a lossy channel. Such hybrid entanglement, which is a key resource for a variety of recently proposed scheme…
A hybrid model of the Deutsch-Jozsa algorithm is presented, inspired by the proposals of hybrid computation by S. Lloyd and P. van Loock et. al. The model is based on two observations made about both the discrete and continuous algorithms already available. First, the Fourier transform is a single-step operation in a continuous-variable (CV) setting. Additionally, any implementation of the oracle is nontrivial in both schemes. The steps of the computation are very similar to those in the CV algorithm, with the main difference being the way in which the qunats, or quantum units of analogic info…
We map the topological properties of a one dimensional superlattice to the optical properties of an electronic system. We find that the nonlinear-optical response is optimized for electrons that live in the transitional morphology between topologically protected edge states and delocalized eigenstates. This provides a novel means of tuning the nonlinear-optical response of hybrid quantum systems. We show how these characteristics can be used to mimic saturable absorption and illustrate how `quantum cords' can be used to build an efficient all-optical switch.
Quantum states and measurements exhibit wave-like --- continuous, or particle-like --- discrete, character. Hybrid discrete-continuous photonic systems are key to investigating fundamental quantum phenomena, generating superpositions of macroscopic states, and form essential resources for quantum-enhanced applications, e.g. entanglement distillation and quantum computation, as well as highly efficient optical telecommunications. Realizing the full potential of these hybrid systems requires quantum-optical measurements sensitive to complementary observables such as field quadrature amplitude an…
We theoretically explore optical bistability for possible signature of all optical switching and their performance in a hybrid quantum optomechanical system comprising of two semiconductor microcavity coupled optically. One of the cavity is driven by an external optical pump laser while the second cavity which contains a quantum dot is indirectly driven by light transmitted from the first cavity. The generated bistable behavior due to optomechanical nonlinearity shows a typical optical switching behavior and it can be controlled by changing the laser power, QD cavity coupling, rocking paramete…
We present two hybrid linear-optical architectures that simultaneously exploit spatial and temporal degrees of freedom of light to effect arbitrary discrete unitary transformations. Our architectures combine the benefits of spatial implementations of linear optics, namely low loss and parallel operation, with those of temporal implementations, namely modest resource requirements and access to transformations of potentially unbounded size. We arrive at our architectures by devising and employing decompositions of large discrete unitary transformations into smaller ones, decompositions we expect…
Here I present my first fiber based coupled optical and EPR experiments associated to the development of a new SiC-YiG quantum sensor that I recently theoretically described (arXiv:1912.11634). This quantum sensor was designed to allow sub-nanoscale single external spin sensitivity optically detected pulsed electron electron double resonance spectroscopy, using an X band pulsed EPR spectrometer, an optical fiber, and a photoluminescence setup. First key experiments before the demonstration of ODPELDOR spectroscopy are presented here. They were performed on a bulk 4H-SiC sample containing an en…
We develop an architecture of hybrid quantum solid-state processing unit for universal quantum computing. The architecture allows distant and nonidentical solid-state qubits in distinct physical systems to interact and work collaboratively. All the quantum computing procedures are controlled by optical methods using classical fields and cavity QED. Our methods have prominent advantage of the insensitivity to dissipation process benefiting from the virtual excitation of subsystems. Moreover, the QND measurements and state transfer for the solid-state qubits are proposed. The architecture opens …
The potential of photon-magnon hybrid systems as building blocks for quantum information science has been widely demonstrated, and it is still the focus of much research. We leverage the strengths of this unique heterogeneous physical system in the field of precision physics beyond the standard model, where the sensitivity to the so-called "invisibles" is currently being boosted by quantum technologies. Here, we demonstrate that quanta of spin waves, driven by tiniest, effective magnetic field, can be detected in a large frequency band using a hybrid system as transducer. This result can be ap…
In the development of atomic, molecular and optical (AMO) physics, atom-ion hybrid systems are characterized by the presence of a new tool in the experimental AMO toolbox: atom-ion interactions. One of the main limitations in state-of-the-art atom-ion experiments is represented by the micromotion component of the ions' dynamics in a Paul trap, as the presence of micromotion in atom-ion collisions results in a heating mechanism that prevents atom-ion mixtures from undergoing a coherent evolution. Here we report the design and the simulation of a novel ion trapping setup especially conceived for…
Low-loss fiber optic links have the potential to connect superconducting quantum processors together over long distances to form large scale quantum networks. A key component of these future networks is a quantum transducer that coherently and bidirectionally converts photons from microwave frequencies to optical frequencies. We present a platform for electro-optic photon conversion based on silicon-organic hybrid photonics. Our device combines high quality factor microwave and optical resonators with an electro-optic polymer cladding to perform microwave-to-optical photon conversion from 6.7 …
