Quantum State Transfer Research Articles

Quantum State Transfer between Superconducting Cavities via Exchange-Free Interactions

Quantum State Transfer between Superconducting Cavities via Exchange-Free Interactions

Design and experimental demonstration of functional devices for energy manipulation in new analog acoustic computers

The development of new analog computers based on analog signals of electromagnetic or elastic waves has become a hot research topic in recent years. In this Letter, based on the concept of quantum state transfer, we study the process of energy transfer between acoustic cavities. Through the transformation from the temporal domain to the spatial domain, we further study the process of energy transfer between acoustic waveguides, and then we realize the applications of energy distributors and limiters in the acoustic system, which are the functional devices of wireless communication technology in new analog acoustic computers. We both simulationlly and experimentally demonstrate the effectiveness of the two applications. The energy distributor and limiter we proposed have the advantages of a relatively wide operating frequency range and adjustability. Our work shows the transfer mechanism of acoustic energy between different structures, which increases its potential application value in new analog acoustic computers.

Quantum state transfer in interacting multiple-excitation systems

Quantum state transfer in interacting multiple-excitation systems

Unlocking the potential of photoexcited molecular electron spins for room temperature quantum information processing

Abstract Future information processing technologies like quantum memory devices have the potential to store and transfer quantum states to enable quantum computing and networking. A central consideration in practical applications for such devices is the nature of the light-matter interface which determines the storage state density and efficiency. Here, we employ an organic radical, α,γ-bisdiphenylene-β-phenylallyl doped into an o-terphenyl host to explore the potential for using tuneable and high-performance molecular media in microwave-based quantum applications. We demonstrate that this radical system exhibits millisecond-long spin-lattice relaxation and microsecond-long phase memory times at room temperature, while also having the capability to generate an oscillating spin-polarized state using a co-dissolved photo-activated tetraphenylporphyrin moiety, all enabled by using a viscous liquid host. This latest system builds upon collective wisdom from previous molecules-for-quantum literature by combining careful host matrix selection, with dynamical decoupling, and photoexcited triplet-radical spin polarisation to realise a versatile and robust quantum spin medium.

Generation of two mode mechanical squeezing induced by nondegenerate parametric amplification

Squeezing light in an optomechanical system involves reducing quantum noise in one of the light’s quadratures through the interaction between optical and mechanical modes. However, achieving successful implementation requires careful control of experimental parameters, which can be challenging. Here, we investigate a two-mode squeezed light transfer from optical to mechanical modes induced by a non-degenerate optical parametric amplifier (OPA). The optomechanical system is driven by frequencies nearly resonant with the anti-stokes fields that can realize cooling mechanical oscillators and quantum state transfer within a resolved sideband (good cavity) limit. Our results show that when a non-degenerate OPA is placed inside the optical cavity, the degree of squeezing in both optical and mechanical modes is significantly enhanced. This leads to the two-mode squeezed light being transferred into two-mode mechanical squeezing in the presence of the non-degenerate OPA under weak optomechanical coupling strength. Interestingly, we found that with negligible thermal bath noise, the two-mode squeezed light completely transferred to yield 50% mirror-mirror squeezing. In contrast, at higher thermal noise, the transfer of squeezed light is weak, causing the system to lose its quantum properties and behave more classically. Furthermore, we have shown that the degree of squeezing in the weak coupling regime drastically decreases with increasing mechanical dissipation rates. We believe that our scheme can achieve strong mechanical squeezing in hybrid optomechanical systems and facilitate homodyne detection to measure the quadratures of the squeezed light.

Parametrically controlled microwave-photonic interface for the fluxonium

Converting quantum information from stationary qubits to traveling photons enables both fast qubit initialization and efficient generation of flying qubits for redistribution of quantum information. This conversion can be performed using cavity-sideband transitions. In the fluxonium, however, direct cavity-sideband transitions are forbidden due to parity symmetry. Here we circumvent this parity selection rule by using a three-wave mixing element to couple the fluxonium to a resonator. We experimentally demonstrate a scheme for interfacing the fluxonium with traveling photons through microwave-induced parametric conversion. We perform fast reset on the fluxonium qubit, initializing it with >95% ground-state population. We then implement controlled release and temporal shaping of a flying photon, useful for quantum state transfer and remote entanglement. The simplicity and flexibility of our demonstrated scheme enables fluxonium-based remote entanglement architectures. Published by the American Physical Society 2024

Disordered Heisenberg XYZ magnetic chains with exponential correlations: Localization and quantum state transfer

Our study investigates the Quantum State Transfer Protocol within a one-dimensional quantum Heisenberg spin chain model that features exponentially correlated disorder in the spin coupling distribution. We conducted extensive numerical simulations to explore how varying degrees of correlation impact the transfer of quantum states through this model of a quantum channel. Our results demonstrate that the extent of correlation significantly influences quantum communication along the channel. Specifically, we observed that in the strongly correlated regime, quantum communication remains largely unaffected even in large systems. These findings are interpreted in the context of the localization properties inherent to the disordered channel.

Quantum teleportation via a hybrid channel and investigation of its success probability

Quantum teleportation enables the transfer of quantum states across any distance and plays a prominent role in quantum communication. In this paper, we theoretically investigate the feasibility of quantum two-qubit teleportation through a hybrid channel consisting of thermal, magnetic, and local components. To study this process, we check the success probability of quantum teleportation and address the quality of the teleported quantum state using fidelity and average fidelity concepts. Furthermore, we examine a crucial quantum aspect of the system, such as the non-Markovianity of the dynamics, by utilizing success probability witness related to the teleported state. Our findings show that this hybrid channel has a good potential to be successful in quantum teleportation.

Shortcut engineering for accelerating topological quantum state transfers in optomechanical lattices

Shortcut engineering for accelerating topological quantum state transfers in optomechanical lattices

Strong quantum state transfer on graphs via loop edges

We quantify the effect of weighted loops at the source and target nodes of a graph on the strength of quantum state transfer between these vertices. We give lower bounds on loop weights that guarantee strong transfer fidelity that works for any graph where this protocol is feasible. By considering local spectral symmetry, we show that the required weight size depends only on the maximum degree of the graph and, in some less favorable cases, the distance between vertices. Additionally, we explore the duration for which transfer strength remains above a specified threshold.

Quantum state transfer between cells and binary tree model

Discussing quantum state transfer on a graph is a very difficult task, when it has a relatively large number of vertices. In this paper, we construct cells so that it contain a number of vertices by partitioning the vertices, so that a finite number of cells can be used to cover all vertices on the graph. Subsequently, we define the adjacency case between cells and the orthonormal basis on the complex Hilbert space. In this framework, the quantum state transfer based on binary tree model is studied by using Laplacian operator.

High-fidelity remote entanglement between superconducting fixed-frequency qubits

Abstract Highly accurate quantum state transfer and remote entanglement between superconducting fixed-frequency qubits have not yet been realized. In this study, we calculate the characteristics of a transmission path with a 1- or 0.25 m superconducting coaxial cable and use the characteristics to perform time evolution simulations of quantum state transfer and remote entanglement between superconducting fixed-frequency qubits. We find that remote entanglement, or half-quantum state transfer, can achieve a high fidelity > 99 % even in the presence of a qubit frequency detuning caused by manufacturing fluctuations, while a small qubit frequency detuning substantially reduces the efficiency of quantum state transfer. Quantum circuit simulations modeling proposed remote entanglement demonstrate that teleportation of a logical qubit with a 3 × 3 surface code, as an example of computation using remote entanglement, attains nearly the same fidelity as in-node computation for both 1- and 0.25 m cable lengths.

Optical Mode Entanglement Generation from an Optomechanical Nanobeam

Abstract Nano-optomechanical systems, capable of supporting enhanced light-matter interactions, have wide applications in studying quantum entanglement and quantum information processors. Yet, preparing optical telecom-band entanglement within a single optomechanical nanobeam remains blank. We propose and design a triply resonant optomechanical nanobeam to generate steady-state entangled propagating optical modes and present its quantum-enhanced performance for teleportation-based quantum state transfer under realistic conditions. Remarkably, the entanglement quantified by logarithmic negativity can obtain E N = 1. Furthermore, with structural imperfections induced by realistic fabrication processes considered, the device still shows great robustness. Together with quantum interfaces between mechanical motion and solid-state qubit processors, the proposed device potentially paves the way for versatile nodes in long-distance quantum networks.

Quantum state transfer in a ring geometry of optical waveguides having nonuniform couplings

The quantum state transfer of a system of N coupled waveguides in a ring geometry, where the last waveguide is coupled to the first one is considered. The coupling parameters are chosen not to be equal, but to vary according to the position of the waveguides. We examine the fidelity between different waveguides in order to check if it is possible to achieve a perfect state transfer (PST). We focused our analysis on the single-photon Fock state and the two-photon N00N state. Very high values of fidelity (> 95%) were found for both cases, but the PST was only observed for the single-photon Fock state.

A dual-species Rydberg array

Large-scale Rydberg atom arrays are used for highly coherent analogue quantum simulations and for digital quantum computations. However, advanced quantum protocols, such as quantum error correction, require midcircuit qubit operations, including the replenishment, reset and read-out of a subset of qubits. A compelling strategy for unlocking these capabilities is a dual-species architecture in which a second atomic species is controlled independently and entangled with the first through Rydberg interactions. Here, we realize a dual-species Rydberg array consisting of rubidium and caesium atoms and explore regimes of interactions and dynamics not accessible in single-species architectures. We achieve enhanced interspecies interactions by electrically tuning the Rydberg states close to a Förster resonance. In this regime, we demonstrate an interspecies Rydberg blockade and implement a quantum state transfer from one species to another. We then generate a Bell state between Rb and Cs hyperfine qubits through an interspecies controlled-phase gate. Finally, we combine interspecies entanglement with a native midcircuit read-out to achieve quantum non-demolition measurements.

Multiplexed quantum state transfer in waveguides

In this article, we consider a realistic waveguide implementation of a quantum network that serves as a testbed to show how to maximize the storage and manipulation of quantum information in QED setups. We analyze two approaches using wavepacket engineering and quantum state transfer protocols. First, we propose and design a family of orthogonal photons in the time domain. These photons allow for a selective interaction with distinct targeted qubits. Yet, mode multiplexing employing resonant nodes is largely spoiled by cross-talk effects. This motivates the second approach, namely, frequency multiplexing. Here we explore the limits of frequency multiplexing through the waveguide, analyzing its capabilities to host and faithfully transmit photons of different frequencies within a given bandwidth. We perform detailed one- and two-photon simulations and provide theoretical bounds for the fidelity of coherent quantum state transfer protocols under realistic conditions. Our results show that state-of-the-art experiments can employ dozens of multiplexed photons with global fidelities fulfilling the requirements imposed by fault-tolerant quantum computing. This is with the caveat that the conditions for single-photon fidelity are met. Published by the American Physical Society 2024

Higher-Dimensional Communications Using Multimode Fibers and Compact Components to Enable a Dense Set of Communicating Channels

Higher-dimensional communications are of interest for multiple reasons, including increasing the classical transmission capacity and, more recently, the quantum state transfer through fibers using the many modes within the fiber. For quantum communications, this enables an increase in the number of bits per photon, increasing quantum fidelity, increasing error thresholds and enabling hyperentanglement transfer, among other possibilities. A high-dimensional quantum state transfer can be transported through multimode fiber using the many modes available. However, this transfer of information through multimode optical fiber is limited by attenuation and mode coupling among the various spatial and polarization modes. Here, we consider how this mode coupling impacts the transfer process. We consider the fiber’s modal properties, including orbital angular momentum, modal group numbers, and principal modes. We also investigate and propose input and output optical components, as well as fiber properties, which better mitigate the deleterious effects of mode coupling. We use the WKB approximation to the scaler wave equation as a guidance to quantify this coupling and then implement corrections to this approximation using exact solutions to the scaler wave equation. We consider methods to circumvent this mode coupling using optical fiber designs, holographic optical components and devices that are commercially available today. Some of these components, such as the holographic gratings and lenses, could be implemented using flat optics.

Quantum state transfer and distribution of past–future correlations in a quantum network

Quantum state transfer and distribution of past–future correlations in a quantum network

Enhanced quantum state transfer and Bell-state generation over long-range multimode interconnects via superadiabatic transitionless driving

Enhanced quantum state transfer and Bell-state generation over long-range multimode interconnects via superadiabatic transitionless driving

Success probabilities in time-reversal-based hybrid quantum state transfer

Success probabilities in time-reversal-based hybrid quantum state transfer