Entanglement is one of the most mysterious and fleeting properties of nature. It is also a powerful resource for quantum information processing. Efforts to design and build a quantum computer are severely constrained by the difficulties of preserving useful qubit entanglement against the environment. Concatenated fault-tolerant error correction provides a framework to perform scalable computation, but is extremely expensive in terms of resources. Direct topological implementations promise robust entanglement and control, but require physical systems with as yet unobserved controllable topological phases. Here we present the first practical scheme for constructing a topological quantum computer based on a 3D cluster state lattice of photons on chip. In contrast to the resource requirements of other schemes, a target error rate of 10^(-16) requires approximately 3000 components per logical qubit. This constitutes a significant advance towards practical quantum computing and leads the way for topological architectures in other implementations.
Entanglement is one of the most mysterious and fleeting properties of nature. It is also a powerful resource for quantum information processing. Efforts to design and build a quantum computer are severely constrained by the difficulties of preserving useful qubit entanglement against the environment. Concatenated fault-tolerant error correction provides a framework to perform scalable computation, but is extremely expensive in terms of resources. Direct topological implementations promise robust entanglement and control, but require physical systems with as yet unobserved controllable topological phases. Here we present the first practical scheme for constructing a topological quantum computer based on a 3D cluster state lattice of photons on chip. In contrast to the resource requirements of other schemes, a target error rate of 10^(-16) requires approximately 3000 components per logical qubit. This constitutes a significant advance towards practical quantum computing and leads the way for topological architectures in other implementations.
The development of a large scale quantum computer is a highly sought after goal of fundamental research and consequently a highly nontrivial problem. Scalability in quantum information processing is not just a problem of qubit manufacturing and control but it crucially depends on the ability to adapt advanced techniques in quantum information theory, such as error correction, to the experimental restrictions of assembling qubit arrays into the millions. In this paper, we introduce a feasible architectural design for large scale quantum computation in optical systems. We combine the recent developments in topological cluster state computation with the photonic module, a simple chip-based device that can be used as a fundamental building block for a large-scale computer. The integration of the topological cluster model with this comparatively simple operational element addresses many significant issues in scalable computing and leads to a promising modular architecture with complete integration of active error correction, exhibiting high fault-tolerant thresholds.
The development of a large scale quantum computer is a highly sought after goal of fundamental research and consequently a highly non-trivial problem. Scalability in quantum information processing is not just a problem of qubit manufacturing and control but it crucially depends on the ability to adapt advanced techniques in quantum information theory, such as error correction, to the experimental restrictions of assembling qubit arrays into the millions. In this paper, we introduce a feasible architectural design for large scale quantum computation in optical systems. We combine the recent developments in topological cluster state computation with the photonic module, a simple chip-based device that can be used as a fundamental building block for a large-scale computer. The integration of the topological cluster model with this comparatively simple operational element addresses many significant issues in scalable computing and leads to a promising modular architecture with complete integration of active error correction, exhibiting high fault-tolerant thresholds.
Optical quantum computation has represented one of the most successful testbed systems for quantum information processing. Along with ion-traps and nuclear magnetic resonance (NMR), experimentalists have demonstrated control of qubits, multi-gubit gates and small quantum algorithms. However, photonic based qubits suffer from a problematic lack of a large scale architecture for fault-tolerant computation which could conceivably be built in the near future. While optical systems are, in some regards, ideal for quantum computing due to their high mobility and low susceptibility to environmental decoherence, these same properties make the construction of compact, chip based architectures difficult. Here we discuss many of the important issues related to scalable fault-tolerant quantum computation and introduce a feasible architecture design for an optics based computer. We combine the recent development of topological cluster state computation with the photonic module, simple chip based devices which can be utilized to deterministically entangle photons. The integration of this operational unit with one of the most exciting computational models solves many of the existing problems with other optics based architectures and leads to a feasible large scale design which can continuously generate a 3D cluster state with a photonic module resource cost linear in the cross sectional size of the cluster.
Topological measurement-based quantum computation (MBQC) enables one to carry out universal fault-tolerant quantum computation via single-qubit measurements with a family of large entangled states called cluster states as resources. Raussendorf's three-dimensional cluster states (RTCSs) based on the surface codes are mainly considered for topological MBQC. In such schemes, however, the logical Hadamard, phase (Z1/2), and T(Z1/4) gates which are essential for building up arbitrary logical gates are not implemented natively without using state distillation or lattice dislocations, to the best of our knowledge. In particular, state distillation generally consumes many ancillary logical qubits; thus it is a severe obstacle against practical quantum computing. To solve this problem, we suggest an MBQC scheme via a family of cluster states called color-code-based cluster states (CCCSs) based on the two-dimensional color codes instead of the surface codes. We define logical qubits, construct elementary logical gates, and describe error correction schemes. We show that all logical Clifford gates generated by the cnot, Hadamard, and phase gates can be implemented natively in a fault-tolerant manner, although the T gate still requires state distillation to be fault-tolerant. The error thresholds of MBQC via CCCSs for logical-Z errors are calculated to be 2.7%--2.8%, which are comparable to the values for RTCSs, assuming a simple error model where physical qubits have nontrivial errors independently with the same probability. We analyze and compare the resource overheads of both the schemes. In particular, we show that the number of physical qubits required for implementing a phase gate with CCCSs is at least about 26 times smaller than with RTCSs using state distillation, for the same code distance.
Quantum error correction (QEC) is crucial for realizing practical quantum computation. However, the fragility of quantum states to environmental noise poses a significant challenge. This work proposes a novel approach to QEC utilizing topological qubits encoded within photonic networks. Topological qubits, characterized by their robust topological properties, offer inherent protection against local perturbations, making them ideal candidates for QEC. This architecture combines the advantages of both topological protection and the scalability offered by photonic networks. We present a theoretical framework for implementing a specific QEC code based on these principles, detailing the encoding process, error detection, and correction operations. The proposed system demonstrates enhanced resilience to noise compared to traditional qubit implementations. Key performance metrics, such as the surface code's logical error rate, are analyzed, highlighting the potential of this approach for achieving fault-tolerant quantum computation. The core of this method lies in the design of a photonic network tailored to efficiently implement the topological code, addressing limitations encountered in conventional qubit systems. Further investigation explores the impact of network topology and photon loss on the overall performance, proposing strategies for mitigating these effects. This research contributes to the ongoing effort to overcome the challenges of QEC and paves the way for building practical, scalable quantum computers.
The possibility of practical large-scale quantum computation is largely dictated by the error threshold and qubit overhead of the error correcting scheme. To achieve this goal, architectures that perform fault tolerance quantum computation (FTQC) with 3D cluster states have been designed; however, the current benchmarks for such constructions are still below general experimental requirements. In light of this, we propose a new 3D FTQC scheme by exploiting geometric tolerance to erasure errors using cluster states with novel lattice structures, specifically, by replacing the physical qubits with small-sized error detection codes that allow simple applications of logical CZ gates. We are able to locate Pauli errors locally and effectively convert them into loss errors. With a combination of code concatenation and multi-staged decoding, the scheme is able to achieve higher performance than traditional cubic lattices in protecting quantum information. We have surveyed a wide range of possible concatenation schemes and Monte-Carlo simulations have been performed on the decoders to study their respective scaling behavior. The scheme has demonstrated an overall decrement in active qubit overhead and an improvement of the error threshold, which varies from 10 % to 160% depending on the noise model, indicating a relatively higher rate of fault tolerance compared with previous cluster states-based codes.