Resource For One-way Quantum Computation Research Articles

Measurement-device-independent quantum secret sharing and quantum conference based on Gaussian cluster state

Cluster state is the basic resource for one-way quantum computation and a valuable resource for establishing quantum network, because it has a flexible and varied composition form. We present measurement-device-independent quantum secret sharing (QSS) and quantum conference (QC) schemes based on continuous variable (CV) four-mode cluster state with different structures. The users of the protocol prepare their own Einstein-Podolsky-Rosen (EPR) states, respectively. One mode of these EPR states is sent to an untrusted relay where a generalized Bell measurement creates different types of CV cluster states among four users, while the other mode is kept at their own station. We show that a shared secret key for QSS and QC schemes is distilled based on the shared quantum correlation among four users. QC and four users QSS are implemented based on the star shape CV cluster state. QSS with three users are implemented based on the linear or square shape CV cluster states. The results show that the secure transmission distance for an asymmetric network, where the transmission distances between the users and relay are different, is longer than that of a symmetric network, where the transmission distances between the users and relay are the same. The presented schemes provide concrete references for establishing quantum network with the CV cluster state.

Connecting two Gaussian cluster states by quantum entanglement swapping.

Cluster state is an important resource for one-way quantum computation and quantum network. In this paper, we present a scheme for connecting two Gaussian cluster states by entanglement swapping, which can be used to connect two local quantum networks composed by cluster states. The connection schemes between different types of four-mode cluster states are analyzed and we show that the structure of the output states after entanglement swapping may be not the same as that of the input states. The entanglement of the obtained new cluster states are presented when suitable feedforward schemes are applied in the entanglement swapping process. By using optimal gains in the classical channel and inseparability criteria, the requirement of squeezing parameters for obtaining entanglement of output states are reduced. The presented scheme provides a concrete reference for constructing quantum networks with cluster states.

Generation of continuous-variable spatial cluster entangled states in optical mode comb

Cluster entangled states are often used as the fundamental resources for one-way quantum computation. In this paper, we put forward a scheme of generating the spatial cluster entangled states of Laguerre–Gaussian modes in a large-Fresnel-number degenerate optical parametric oscillator operating below threshold with type I phase matching, which is pumped by two spatial Laguerre–Gaussian modes with the same frequency. The nonlinear parametric process of each pump mode satisfies momentum, energy, and orbit angular momentum conservation. Eleven-partite spatial cluster entangled states of Laguerre–Gaussian modes can be produced in the optical mode comb under feasible experimental condition, which can be demonstrated by using the entanglement criterion proposed by van Loock and Furusawa.

One-Way Quantum Computation with Cluster State and Probabilistic Gate

We present a scheme for efficiently constructing a two-dimensional cluster state, which serves as the central physical resource for one-way quantum computation. In this scheme, we successfully make the required computational overhead scale efficiently with the qubit number by using a probabilistic entangling quantum gate.

Large-scale cluster state generation with nuclear spins in diamonds

The cluster state is an indispensable resource for one-way quantum computing (1WQC). We propose a practical scheme for constructing cluster states among nuclear spins in nitrogen-vacancy defect centres (NV centres) in different diamonds. The entanglement of nuclear spins within an NV centre is made by hyperfine coupling via electron spin, and the entanglement between remote NV centres is accomplished using the parity projection of emitted photons. We discus the possibility to build large-scale nuclear-spin cluster states with diamonds.

Optical one-way quantum computing with a simulated valence-bond solid

One-way quantum computing requires an entangled multiqubit system. So-called cluster states have been proposed to provide this resource, but they are difficult to generate. An alternative that uses the ground state of a one-dimensional chain of spins is now experimentally realized and used to construct a quantum logic gate. One-way quantum computation proceeds by sequentially measuring individual spins in an entangled many-spin resource state1. It remains a challenge, however, to efficiently produce such resources. Is it possible to reduce the task of their production to simply cooling a quantum many-body system to its ground state? Cluster states, the canonical resource for one-way quantum computing, do not naturally occur as ground states of physical systems2,3, leading to a significant effort to identify alternatives that do appear as ground states in spin lattices 4,5,6,7,8. An appealing candidate is a valence-bond-solid state described by Affleck, Kennedy, Lieb and Tasaki9 (AKLT). It is the unique, gapped ground state for a two-body Hamiltonian on a spin-1 chain, and can be used as a resource for one-way quantum computing 4,5,6,7. Here, we experimentally generate a photonic AKLT state and use it to implement single-qubit quantum logic gates.

Measurement Based Quantum Computation on Fractal Lattices

In this article we extend on work which establishes an analology between one-way quantum computation and thermodynamics to see how the former can be performed on fractal lattices. We find fractals lattices of arbitrary dimension greater than one which do all act as good resources for one-way quantum computation, and sets of fractal lattices with dimension greater than one all of which do not. The difference is put down to other topological factors such as ramification and connectivity. This work adds confidence to the analogy and highlights new features to what we require for universal resources for one-way quantum computation.

Cluster states from imperfect global entanglement

The cluster state, the highly entangled state that is the central resource for one-way quantum computing, can be efficiently generated in a variety of physical implementations via global nearest-neighbor interactions. In practice, a systematic phase error is expected in the entangling process, resulting in imperfect cluster states. We present a stochastic measurement technique to generate large perfect cluster states and other graph states with high probability from imperfect cluster states even when their initial entanglement is weak.

Distributed quantum-information processing with minimal local resources

We present a protocol for growing graph states, the resource for one-way quantum computing, when the available entanglement mechanism is highly imperfect. The distillation protocol is frugal in its use of ancilla qubits, requiring only a single ancilla qubit when the noise is dominated by one Pauli error, and two for a general noise model. The protocol works with such scarce local resources by never postselecting on the measurement outcomes of purification rounds. We find that such a strategy causes fidelity to follow a biased random walk, and that a target fidelity is likely to be reached more rapidly than for a comparable postselecting protocol. An analysis is presented of how imperfect local operations limit the attainable fidelity. For example, a single Pauli error rate of $20%$ can be distilled down to $\ensuremath{\sim}10$ times the imperfection in local operations.

Comment on “Efficient high-fidelity quantum computation using matter qubits and linear optics”

Recently Barrett and Kok (BK) proposed an elegant method for entangling separated matter qubits. They outlined a strategy for using their entangling operation (EO) to build graph states, the resource for one-way quantum computing. However by viewing their EO as a graph fusion event, one perceives that each successful event introduces an ideal redundant graph edge, which growth strategies should exploit. For example, if each EO succeeds with probability p=0.4 then a highly connected graph can be formed with an overhead of only about ten EO attempts per graph edge. The BK scheme then becomes competitive with the more elaborate entanglement procedures designed to permit p to approach unity.