Quantum Information Transfer Research Articles

Time-reversal-symmetry breaking and chiral quantum state manipulation in plasmonic nanorings

The chiral transfer of quantum information in a metal nanoring network is presented. A system of three metal nanorings coupled to a two-level quantum dot enables the chiral transport of quantum states by breaking the time-reversal symmetry, which provides a platform for chiral quantum information processing in nanorings. The direction of the chirality can be controlled by preparing the quantum dot in its ground or excited state. We show that the system dynamics can be controlled such that one can achieve a perfect or a partial chiral transfer of the excitation. The synthetic magnetic field that enables the chirality in the system makes the generation of specifically tailored entangled nanoring states possible. As particular examples, we show that in this platform the generation of a two-excitation NOON state and entangled coherent states among nanorings can be realized.

Realization of Tunable Highly-Efficient Quantum Routing in Chiral Waveguides

The chiral interaction between single photons in waveguides and quantum emitters has gained considerable attention. Here, we proposed a tunable quantum routing scheme with a chiral quantum system by coupling an emitter to two chiral waveguides. Conventional quantum routers can only be achieved with each port output probability no larger than 25%. But our scheme can transfer quantum information arbitrarily from an input port to another, and each port’s output probability is 100%. Besides, we investigated the influence of the Purcell factor in quantum routing properties. No matter how to change the size of the directionalities Sj or set a specific value to the dissipation of the emitter, we always found that the quantum routing has very high efficiency. Moreover, we also used a superconducting qubit coupled to two resonators to show the present scheme is pretty feasible for experimental implementation.

Quantum Information Transformation from One Particle onto another Particle by Using Hybrid and Hyper Entangled States

In this paper, we propose two protocols for the transfer of quantum information carried by one particle onto another particle by using the path-spin hybrid and hyper entangled states as the quantum resources. It has been shown that the double slit arrangement with a spin flipper at one of its openings can be used for the generation of path-spin hybrid and hyper entangled states. By using such path-spin entangled states as the quantum resource, the quantum information encoded in one particle is transferred to another particle via spin and path measurements.

Quantum information transfer using weak measurements and any non-product resource state

Information about an unknown quantum state can be encoded in weak values of projectors belonging to a complete eigenbasis. A protocol that enables one party—Bob—to remotely determine the weak values corresponding to weak measurements performed by another spatially separated party—Alice is presented. The particular set of weak values contains complete information of the quantum state encoded on Alice’s register, which enacts the role of preselected system state in the aforementioned weak measurement. Consequently, Bob can determine the quantum state from these weak values, which can also be termed as remote state determination or remote state tomography. A combination of non-product bipartite resource state shared between the two parties and classical communication between them is necessary to bring this statistical scheme to fruition. Significantly, the information transfer of a pure quantum state of any known dimensions can be effected even with resource states of low dimensionality and purity with a single measurement setting at Bob’s end.

Quantum information transfer between optical and microwave output modes via cavity magnonics

The transfer of quantum information between the output propagating microwave mode and the radiation that emerges out from the hybrid quantum source through cavity magnonics has been investigated in detail. To examine the quantum optical properties of the system, we employed the input–output theory. We note that significant amounts of quantum entanglement, coherent information-distillable entanglement bits transfer and the Gaussian quantum discord between the output optical and microwave modes are obtained from the proposed quantum source. It is found that the Gaussian quantum discord bounds the quantum entanglement and coherent information. Furthermore, we found that the Gaussian quantum discord is the best quantifier of the source to capture the quantum correlations of the source other than the quantum entanglement and coherent information.

Bidirectional Controlled Teleportation of Two-qubit and Three-qubit State via Nine-qubit Entangled State

In this paper, a bidirectional controlled quantum teleportation via a nine-qubit entangled state is given. In this scheme, Alice wants to teleport a two-qubit entangled state to Bob and Bob wants to teleport arbitrary three-qubit state to Alice at the same time. The quantum teleportation is supervised by a controller. We firstly product a nine-qubit entangled states by the states |000000000⟩, and then we use this entangled states as quantum channel to transfer quantum information along three nodes. This scheme is efficient and economical because the intrinsic efficiency reaches 5/19.

Tailoring Wavelength- and Emitter-Orientation-Dependent Propagation of Single Photons in Silicon Nanowires

Designing the propagation of single quanta at subwavelength scale is of major interest for integrated optical quantum information transfer. This study demonstrates the high potential of crystalline silicon wires with nanometric sections as low-loss nanochannels for quantum nanophotonics. Single photons from N-$V$ centers in nanodiamonds can be guided and spectrally filtered over several micrometers while conserving their quantum statistics. Moreover, these nanowaveguides can be designed so that only light from emitters of specific orientations is efficiently guided, enabling quantum state selectivity and modal control of single-photon transfer in subwavelength waveguides.

Quantum protocols at presence of nonabelian superselection rules in the framework of algebraic model

In this paper, we study the influence of nonabelian superselection rules on the transfer of quantum information with the help of qubits on the base of an algebraic model and formulate quantum protocols. We pay the main attention to the superselection structure of the algebra of observables [Formula: see text] defined by the Cuntz algebra [Formula: see text] (a field algebra) that contains [Formula: see text] as a pointwise fixed subalgebra with respect to the action of the gauge group [Formula: see text]. We prove that it is possible to code information only with the help of states such that projectors on them belong to the algebra of observables. These projectors commute with the elements of the representation of the group [Formula: see text], and therefore allow the recipient to restore the obtained information.

Transfer of quantum information via a dissipative protocol for data classification

We consider the equilibration dynamics of a two-level quantum system in contact with multiple structured reservoirs that carry quantum information. We develop a micromaser-like quantum master equation based on repeated interactions and show that some information is transferred from the quantum reservoir into the quantum system in the steady-state. In the results we obtained from the analytical methods we used, we have developed a clear expression of the information transferred to the two-level system in terms of information reservoir parameters and interaction coefficients of the probe qubit with the reservoirs. We propose an open quantum classifier model by developing a binary classification rule by use of these results. We also develop the analytical description of the classification process by quantum parameter estimation.

Quantum communication with itinerant surface acoustic wave phonons

Surface acoustic waves are commonly used in classical electronics applications, and their use in quantum systems is beginning to be explored, as evidenced by recent experiments using acoustic Fabry–Pérot resonators. Here we explore their use for quantum communication, where we demonstrate a single-phonon surface acoustic wave transmission line, which links two physically separated qubit nodes. Each node comprises a microwave phonon transducer, an externally controlled superconducting variable coupler, and a superconducting qubit. Using this system, precisely shaped individual itinerant phonons are used to coherently transfer quantum information between the two physically distinct quantum nodes, enabling the high-fidelity node-to-node transfer of quantum states as well as the generation of a two-node Bell state. We further explore the dispersive interactions between an itinerant phonon emitted from one node and interacting with the superconducting qubit in the remote node. The observed interactions between the phonon and the remote qubit promise future quantum-optics-style experiments with itinerant phonons.

Transferring Quantum Information through the Quantum Channel using Synchronous Multiplexing for Multiple users

Transferring Quantum Information through the Quantum Channel using Synchronous Multiplexing for Multiple users

Interplay of charge noise and coupling to phonons in adiabatic electron transfer between quantum dots

Long-distance transfer of quantum information in architectures based on quantum dot spin qubits will be necessary for their scalability. One way of achieving it is to simply move the electron between two quantum registers. Precise control over the electron shuttling through a chain of tunnel-coupled quantum dots is possible when interdot energy detunings are changed adiabatically. Deterministic character of shuttling is however endangered by coupling of the transferred electron to thermal reservoirs: sources of fluctuations of electric fields, and lattice vibrations. We theoretically analyse how the electron transfer between two quantum dots is affected by electron-phonon scattering, and interaction with sources of $1/f$ and Johnson charge noise in both detuning and tunnel coupling. The electron-phonon scattering turns out to be irrelevant in Si quantum dots, while a competition between the effects of charge noise and Landau-Zener effect leads to an existence of optimal detuning sweep rate, at which probability of leaving the electron behind is minimal. In GaAs quantum dots, on the other hand, coupling to phonons is strong enough to make the phonon-assisted processes of interdot transfer dominate over influence of charge noise. The probability of leaving the electron behind depends then monotonically on detuning sweep rate, and values much smaller than in silicon can be obtained for slow sweeps. However, after taking into account limitations on transfer time imposed by need for preservation of electron's spin coherence, minimal probabilities of leaving the electron behind in both GaAs- and Si-based double quantum dots turn out to be of the same order of magnitude. Bringing them down below $10^{-3}$ requires temperatures $\leq \! 100$ mK and tunnel couplings above $20$ $\mu$eV.

Catalytic Quantum Teleportation.

In this work, we address fundamental limitations of quantum teleportation-the process of transferring quantum information using classical communication and preshared entanglement. We develop a new teleportation protocol based upon the idea of using ancillary entanglement catalytically, i.e., without depleting it. This protocol is then used to show that catalytic entanglement allows for a noiseless quantum channel to be simulated with a quality that could never be achieved using only entanglement from the shared state, even for catalysts with a small dimension. On the one hand, this allows for a more faithful transmission of quantum information using generic states and fixed amount of consumed entanglement. On the other hand, this shows, for the first time, that entanglement catalysis provides a genuine advantage in a generic quantum-information processing task. Finally, we show that similar ideas can be directly applied to study quantum catalysis for more general problems in quantum mechanics. As an application, we show that catalysts can activate so-called passive states, a concept that finds widespread application, e.g., in quantum thermodynamics.

Quantum networks based on color centers in diamond

With the ability to transfer and process quantum information, large-scale quantum networks will enable a suite of fundamentally new applications, from quantum communications to distributed sensing, metrology, and computing. This Perspective reviews requirements for quantum network nodes and color centers in diamond as suitable node candidates. We give a brief overview of state-of-the-art quantum network experiments employing color centers in diamond and discuss future research directions, focusing, in particular, on the control and coherence of qubits that distribute and store entangled states, and on efficient spin–photon interfaces. We discuss a route toward large-scale integrated devices combining color centers in diamond with other photonic materials and give an outlook toward realistic future quantum network protocol implementations and applications.

Vectorial polaritons in the quantum motion of a levitated nanosphere

The strong coupling between elementary excitations of the electromagnetic field (photons) and quantized mechanical vibrations (phonons) produces hybrid quasi-particle states, known as phonon-polaritons. Their typical signature is the avoided crossing between the eigenfrequencies of the coupled system, as paradigmatically illustrated by the Jaynes-Cummings Hamiltonian, and observed in quantum electrodynamics experiments where cavity photons are coupled to atoms, ions, excitons, spin ensambles and superconducting qubits. In this work, we demonstrate the generation of phonon-polaritons in the quantum motion of an optically-levitated nanosphere. The particle is trapped in high vacuum by an optical tweezer and strongly coupled to a single cavity mode by coherent scattering of the tweezer photons. The two-dimensional motion splits into two nearly-degenerate components that, together with the optical cavity mode, define an optomechanical system with three degrees-of-freedom. As such, when entering the strong coupling regime, we observe hybrid light-mechanical states with a dispersion law typical of tripartite quantum systems. Remarkably, the independent components of motion here identify a physical vibration direction on a plane that, similarly to the polarization of light, confers a vectorial nature to the polariton field. Our results pave the way to novel protocols for quantum information transfer between photonic and phononic components and represent a key-step towards the demonstration of optomechanical entangled states at room temperature.

Dynamical characterization of quadrupole topological phases in superconducting circuits

The recent experimental realization of a programmable two-dimensional square superconducting qubit array opens a new avenue for quantum simulation with qubits [Science 372, 948 (2021)]. Here, we present an experimentally feasible method to achieve two-dimensional superconducting qubit lattice with tunable coupling strengths. A configuration with higher-order topological phases is constructed, featuring topologically protected boundary states in lower dimension (corner states). We show that the quadrupole topological phases can be effectively characterized by the dynamics of the single-excitation quantum state. Moreover, we also explore the detection and dynamics of the corner modes in our qubit lattice system. Particularly, we propose an effective scheme to realize quantum information transfer via the corner states. Our work suggests that superconducting circuits systems are a fertile platform to study novel topological quantum phases and may shed light on the ongoing exploration of topologically protected quantum information processing.

Optimal State Transfer and Entanglement Generation in Power-Law Interacting Systems.

We present an optimal protocol for encoding an unknown qubit state into a multiqubit Greenberger-Horne-Zeilinger-like state and, consequently, transferring quantum information in large systems exhibiting power-law interactions. For all power-law exponents between and , where is the dimension of the system, the protocol yields a polynomial speed-up for and a superpolynomial speed-up for , compared to the state of the art. For all , the protocol saturates the Lieb-Robinson bounds (up to subpolynomial corrections), thereby establishing the optimality of the protocol and the tightness of the bounds in this regime. The protocol has a wide range of applications, including in quantum sensing, quantum computing, and preparation of topologically ordered states. In addition, the protocol provides a lower bound on the gate count in digital simulations of power-law interacting systems.

Piezoacoustics for precision control of electrons floating on helium

Piezoelectric surface acoustic waves (SAWs) are powerful for investigating and controlling elementary and collective excitations in condensed matter. In semiconductor two-dimensional electron systems SAWs have been used to reveal the spatial and temporal structure of electronic states, produce quantized charge pumping, and transfer quantum information. In contrast to semiconductors, electrons trapped above the surface of superfluid helium form an ultra-high mobility, two-dimensional electron system home to strongly-interacting Coulomb liquid and solid states, which exhibit non-trivial spatial structure and temporal dynamics prime for SAW-based experiments. Here we report on the coupling of electrons on helium to an evanescent piezoelectric SAW. We demonstrate precision acoustoelectric transport of as little as ~0.01% of the electrons, opening the door to future quantized charge pumping experiments. We also show SAWs are a route to investigating the high-frequency dynamical response, and relaxational processes, of collective excitations of the electronic liquid and solid phases of electrons on helium.

Quantum simulations with multiphoton Fock states

Quantum simulations are becoming an essential tool for studying complex phenomena, e.g. quantum topology, quantum information transfer and relativistic wave equations, beyond the limitations of analytical computations and experimental observations. To date, the primary resources used in proof-of-principle experiments are collections of qubits, coherent states or multiple single-particle Fock states. Here we show a quantum simulation performed using genuine higher-order Fock states, with two or more indistinguishable particles occupying the same bosonic mode. This was implemented by interfering pairs of Fock states with up to five photons on an interferometer, and measuring the output states with photon-number-resolving detectors. Already this resource-efficient demonstration reveals topological matter, simulates non-linear systems and elucidates a perfect quantum transfer mechanism which can be used to transport Majorana fermions.

Robust single-qubit gates by composite pulses in three-level systems

Composite pulses are an efficient tool for robust quantum control. In this work, we derive the form of the composite pulse sequence to implement robust single-qubit gates in a three-level system, where two low-energy levels act as a qubit. The composite pulses can efficiently cancel the systematic errors up to a certain order. We find that the three-pulse sequence cannot completely eliminate the first order of systematic errors, but still availably makes the fidelity resistant to variations in a specific direction. When employing more pulses in the sequence ($N>3$), the fidelity can be insensitive to the variations in all directions and the robustness region becomes much wider. Finally we demonstrate the applications of composite pulses in quantum information processing, e.g., robust quantum information transfer between two qubits.