Preparation Of Cluster States Research Articles

Multicast-based fault-tolerant multiparty state preparation of four-qubit cluster states

The primary aim of this study is to utilize multicast in the preparation of multi-party four-qubit cluster states. In the presence of environment noises, errors may influence the procedure of the particle distribution. To address this challenge, we propose a fault-tolerant scheme to manage the errors within the detectable channel particles. Based on the Bell chain channel, our approach could prepare arbitrary four-particle cluster state by introducing auxiliary particles, where the receiver performs the unitary operation for recovering the target states. Compared to previous multicast protocols, our scheme reduces resource consumption and operational complexity during cluster state preparation. Additionally, we analyze the system’s fidelity in incoherent environments, providing a more comprehensive understanding of the impact of noise on quantum communication systems.

Chemically aware unitary coupled cluster with abinitio calculations on an ion trap quantum computer: A refrigerant chemicals' application.

Circuit depth reduction is of critical importance for quantum chemistry simulations on current and near term quantum computers. This issue is tackled by introducing a chemically aware strategy for the unitary coupled cluster ansatz. The objective is to use the chemical description of a system to aid in the synthesis of a quantum circuit. We combine this approach with two flavors of symmetry verification for the reduction of experimental noise. These methods enable the use of Quantinuum's System Model H1 ion trap quantum computer for a 6-qubit quantum subspace expansion calculation. We present (i) calculations to obtain methane's optical spectra; (ii) an atmospheric gas reaction simulation involving [CH3⋅-H-OH]‡. Using our chemically aware unitary coupled cluster state-preparation strategy in tandem with state of the art symmetry verification methods, we improve device yield for CH4 at 6 qubits. This is demonstrated by a 90% improvement in two-qubit gate count and a reduction in relative error to 0.2% for electronic energy calculated on System Model H1.

Symmetric Finite-Time Preparation of Cluster States via Quantum Pumps.

It has recently been established that clusterlike states-states that are in the same symmetry-protected topological phase as the cluster state-provide a family of resource states that can be utilized for measurement-based quantum computation. In this Letter, we ask whether it is possible to prepare clusterlike states in finite time without breaking the symmetry protecting the resource state. Such a symmetry-preserving protocol would benefit from topological protection to errors in the preparation. We answer this question in the positive by providing a Hamiltonian in one higher dimension whose finite-time evolution is a unitary that acts trivially in the bulk, but pumps the desired cluster state to the boundary. Examples are given for both the 1D cluster state protected by a global symmetry, and various 2D cluster states protected by subsystem symmetries. We show that even if unwanted symmetric perturbations are present in the driving Hamiltonian, projective measurements in the bulk along with feed-forward correction is sufficient to recover a clusterlike state.

A proposal for preparation of cluster states with linear optics* *Project supported by the National Natural Science Foundation of China (Grant Nos. 12025401 and U1930402).

Measurement-based quantum computation in an optical setup shows great promise towards the implementation of large-scale quantum computation. The difficulty of measurement-based quantum computation lies in the preparation of cluster state. In this paper, we propose the method of generating the large-scale cluster state, which is a platform for measurement-based quantum computation. In order to achieve more complex quantum circuits, the preparation protocol of N-photon cluster state will be proposed as a generalization of the preparation of four- and five-photon cluster states. Furthermore, our proposal is experimentally feasible.

Controlled Secure Direct Communication Protocol via the Three-qubit Partially Entangled Set of States

In this paper, we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme, which was found insecure under two kinds of attacks, fake entangled particles attack and disentanglement attack. Then, by changing the party of the preparation of cluster states and using unitary operations, we present an improved protocol which can avoid these two kinds of attacks. Moreover, the protocol is proposed using the three-qubit partially entangled set of states. It is more efficient by only using three particles rather than four or even more to transmit one bit secret information. Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource, it makes this protocol more convenient from an applied point of view.

Preparation of the Cluster States in a Linear Trap Systems

A scheme for the preparation of four-ion entangled cluster states has been proposed. Two two-level ions are confined in a linear trap and are simultaneously driven with a laser beam. In the Lamb-Dicke regime, we can get the effective Hamiltonian in the interaction picture.The effective Hamiltonian may be used to describe a realistic physical system. The scheme is insensitive to both the initial vibrational state and heating.

Error Sensitivity to Environmental Noise in Quantum Circuits for Chemical State Preparation.

Calculating molecular energies is likely to be one of the first useful applications to achieve quantum supremacy, performing faster on a quantum than a classical computer. However, if future quantum devices are to produce accurate calculations, errors due to environmental noise and algorithmic approximations need to be characterized and reduced. In this study, we use the high performance qHiPSTER software to investigate the effects of environmental noise on the preparation of quantum chemistry states. We simulated 18 16-qubit quantum circuits under environmental noise, each corresponding to a unitary coupled cluster state preparation of a different molecule or molecular configuration. Additionally, we analyze the nature of simple gate errors in noise-free circuits of up to 40 qubits. We find that, in most cases, the Jordan-Wigner (JW) encoding produces smaller errors under a noisy environment as compared to the Bravyi-Kitaev (BK) encoding. For the JW encoding, pure dephasing noise is shown to produce substantially smaller errors than pure relaxation noise of the same magnitude. We report error trends in both molecular energy and electron particle number within a unitary coupled cluster state preparation scheme, against changes in nuclear charge, bond length, number of electrons, noise types, and noise magnitude. These trends may prove to be useful in making algorithmic and hardware-related choices for quantum simulation of molecular energies.

Cluster state entanglement generation and concentration on nitrogen-vacancy centers in decoherence-free subspace

Exploiting the composite system in which two nitrogen-vacancy centers coupled to a microtoroid resonator, we proposed the cluster state entanglement generation and concentration schemes on nitrogen-vacancy centers in decoherence-free subspace. The proposed system is well suited for the systematic preparation of cluster states in one-way quantum computation due to the controllability and scalability. Accompanied with the optimal entanglement concentration protocol for the logic-qubit expanded cluster state, one can efficiently preserve the maximal entanglement. We discussed the experimental feasibility of our schemes by considering the currently available techniques, and believe that the schemes may be useful in further solid-state quantum information processing.

Fidelity of measurement-based quantum computation in a bosonic environment

We investigate the fidelity of the measurement-based quantum computation (MBQC) when it is coupled with boson environment, by measuring cluster state fidelity and gate fidelity. Two different schemes of cluster state preparation are studied. In the Controlled-Z (CZ) creation scheme, cluster states are prepared by entangling all qubits in $|+\rangle$ state with CZ gates on all neighboring sites. The fidelity shows an oscillation pattern over time evolution. The influence of environment temperature is evaluated, and suggestions are given to enhance the performance of MBQC realized in this way. In the Hamiltonian creation scheme, cluster states are made by cooling a system with cluster Hamiltonians, of which ground states are cluster states. The fidelity sudden drop phenomenon is discovered. When the coupling is below a threshold, MBQC systems are highly robust against the noise. Our main environment model is the one with a single collective bosonic mode.

Preparation of multipartite entangled states used for quantum information networks

The preparation of multipartite entangled states is the prerequisite for exploring quantum information networks and quantum computation. In this paper, we review the experimental progress in the preparation of cluster states and multi-color entangled states with continuous variables. The preparation of lager scale multipartite entangled state provide valuable quantum resources to implement more complex quantum informational tasks.

Preparation of cluster states with endohedral fullerenes in single-walled carbon nanotubes

We propose two scalable methods for generation of cluster states with arrays of endohedral fullerenes 15N@C60 residing in single-walled carbon nanotubes (SWCNTs) using direct and indirect methods, respectively. The direct method makes use of a series of controlled-phase flip (CPF) gates by electron spin resonance pulses of selective frequencies and durations, where the CPF gates are realized by magnetic-dipole couplings between the electron spins of the nearest-neighbour fullerenes in SWCNTs. The indirect method resorts to auxiliary mobile electron as the flying qubit, which transfers quantum information from one site to another. This greatly releases the requirements for the distance between fullerenes in SWCNTs. The decoherence effect and experimental feasibility are also discussed based on currently available technology.

Preparation of cluster states with trapped electrons on a liquid helium surface

We present a scheme for the preparation of one-dimensional (1D) and two-dimensional (2D) cluster states with electrons trapped on a liquid helium surface and driven by a classical laser beam. The two lowest levels of the vertical motion of the electron act as a two-level system, and the quantized vibration of the electron along one of the parallel directions (the x direction) serves as the bosonic mode. The degrees of freedom of the vertical and parallel motions of the trapped electron can be coupled together by a classical laser field. With the proper frequency of the laser field, the cluster states can be realized.

Deterministic controlled-phase gate and preparation of cluster states via singly charged quantum dots in cavity quantum electrodynamics

A controlled-phase gate is constructed deterministically in a quantum dot (QD)-cavity system based on Faraday rotation via singly charged QDs in the strong-coupling regime. The fidelity of the gate can reach relatively high values even if cavity decay and leakage are considered. Furthermore, we present two schemes for implementing N-qubit cluster states for electron spins and photons, respectively, by exploiting this gate. The schemes are very simple and can be easily realized in the current experiment.

Eliminating Next-Nearest-Neighbor Interactions in the Preparation of Cluster State

By analyzing recent schemes for preparing the chain cluster state, we find that the existence of long-range couplings between qubits will induce a quick decay of the fidelity of the cluster state. We propose some schemes for eliminating the effect of the next-nearest-neighbor interactions in the XY and Ising models by dynamical decoupling method. In our approach, the undesired next-nearest-neighbor interactions are effectively suppressed and the fidelity of the generated cluster state is greatly improved by the pulse operations.

Preparation of Cluster States of Atomic Qubits in Cavity QED

We propose an optical scheme to generate cluster states of atomic qubits, with each trapped in separate optical cavity, via atom-cavity-laser interaction. The quantum information of each qubit is encoded on the degenerate ground states of the atom, hence the entanglement between them is relatively stable against spontaneous emission. A single-photon source and two classical fields are employed in the present scheme. By controlling the sequence and time of atom-cavity-laser interaction, we show that the atomic cluster states can be produced deterministically.

Cluster State Entanglement of Semiconductor Quantum Dots Based on Faraday Rotation

We propose a scheme for a large-scale cluster state preparation of single-charged semiconductor quantum dots utilizing Faraday rotation. Without interaction between quantum dots, the exciton induced Faraday rotation could distribute the spatially separate quantum dots into a quantum network assisted by cavity QED. We obtain the corresponding parameters from the numerical simulation based on the input-output process for the required Faraday rotation and some discussion is made in view of experimental feasibility.

Preparation of cluster states of four distant atoms by the interference of polarized photons

We propose a protocol to generate the cluster states of four A-type three-level atoms trapped in distant cavities by using the interference of polarized photons. The protocol uses the effects of the quantum statistics of indistinguishable photons emitted by the atoms inside optical cavities. This makes the protocol more realizable in experiments.

Preparation of cluster state in large detuned cavity

An experimentally realizable physical scheme for preparing multiqubit cluster states from a large detuned atom–cavity interaction is proposed. The scheme is free of any type of measurement and insensitive to the cavity decay, and the cavity field is only virtually excited so that there is no information exchanging between atom and cavity. The time required for the gate operations is very short, which is important for decoherence. We also discuss the experimental feasibility of our scheme.

Schemes for Greenberger–Horne–Zeilinger and cluster state preparation**The project is supported by the National Natural Science Foundation of China under Grant No 10575017.

Schemes to generate Greenberger–Horne–Zeilinger (GHZ) and cluster states of three atoms are proposed in a two-mode cavity. The advantages of the schemes are their robustness against decoherence due to spontaneous emission of the excited states and decay of the cavity modes. Moreover, the schemes can be generalized to generate N-atom entangled states.

Practical effects in the preparation of cluster states using weak non-linearities

We discuss experimental effects in the implementation of a recent scheme for performing bus mediated entangling operations between qubits. Here a bus mode, a strong coherent state, successively undergoes weak Kerr-type non-linear interactions with qubits. A quadrature measurement on the bus then projects the qubits into an entangled state. This approach has the benefit that entangling gates are non-destructive, may be performed non-locally, and there is no need for efficient single photon detection. In this paper we examine practical issues affecting its experimental implementation. In particular, we analyze the effects of post-selection errors, qubit loss, bus loss, mismatched coupling rates and mode-mismatch. We derive error models for these effects and relate them to realistic fault-tolerant thresholds, providing insight into realistic experimental requirements.