Large Scale Modular Quantum Computer Architecture with Atomic Memory and Photonic Interconnects (1208.0391v2)

Abstract: The practical construction of scalable quantum computer hardware capable of executing non-trivial quantum algorithms will require the juxtaposition of different types of quantum systems. We analyze a modular ion trap quantum computer architecture with a hierarchy of interactions that can scale to very large numbers of qubits. Local entangling quantum gates between qubit memories within a single register are accomplished using natural interactions between the qubits, and entanglement between separate registers is completed via a probabilistic photonic interface between qubits in different registers, even over large distances. We show that this architecture can be made fault-tolerant, and demonstrate its viability for fault-tolerant execution of modest size quantum circuits.

• The paper presents MUSIQC, a large-scale modular quantum computer architecture combining trapped ion registers for local gates with photonic interconnects for remote entanglement.
• The architecture uses Elementary Logic Units (ELUs) as ion trap registers linked by photonic interfaces and optical switches, employing probabilistic entanglement between ELUs.
• This modular design supports fault tolerance and theoretically enables scaling to millions of qubits using current ion trapping and quantum photonics technology.

Overview of Modular Quantum Computer Architecture with Atomic Memory and Photonic Interconnects

The paper presents an in-depth analysis of a large-scale modular quantum computer architecture that integrates atomic ion qubit memories with photonic interconnects. This structure aims to overcome the challenge of scalability in quantum computation by employing a hierarchical interaction model. Within this framework, entangling gates are performed locally through natural qubit interactions, while remote entanglement between separate registers is facilitated probabilistically via photonic interfaces. This essay details the significant results, architecture design, and potential impact on quantum computing paradigms.

The proposed Modular Universal Scalable Ion Trap Quantum Computer (MUSIQC) exhibits potential for scaling to millions of qubits by using two main components: trapped ion multi-qubit registers and photonic interconnects for flexible, long-distance connectivity. The architecture leverages ion trap technology for high coherence, which is essential for effective quantum memories, along with well-established techniques for initializing and detecting qubit states with high fidelity.

Architecture Design

The architecture is organized into Elementary Logic Units (ELUs), wherein each ELU functions as a register of around 10 to 100 qubits. The register facilitates entangling quantum gates locally using phonon-mediated interactions. Meanwhile, the interfacing architecture links distinct ELUs through photonic channels. This is conducted via optical crossconnect switches that enable reconfigurable connections across the quantum network.

The ELUs leverage the quantum charge-coupled device (QCCD) approach for ion shuttling between local regions within larger multiplexed traps. This supports the realization of modest-scale quantum circuits. Furthermore, the paper addresses the complexity management by articulating strategies for error correction and overall architectural efficiency.

Entanglement and Fault Tolerance

Entanglement between qubits in different ELUs is probabilistically achieved by photonic means, via two distinct approaches: type I and type II interferences. Type I involves weak excitation leading to single-photon emissions, while type II relies on single-photon emissions with distinguishable internal properties like polarization.

This modular structure supports fault-tolerant operations, even when probabilistic entanglement has a significant latency compared to local gate operations. It ensures scalability through techniques that maintain low error rates across diverse operational conditions. Remarkably, the architecture theoretically operates under any ratio of entanglement time to coherence time, with reasonable qubit overhead adjustments.

Implications and Future Perspectives

The MUSIQC architecture highlights practical scalability with existing technologies in ion trapping and quantum photonics. The discussion anticipates realistic implementations requiring advancements in micrometer-scale ion trap structures, integrated optics, and control systems. This work underlines the need for cross-disciplinary technological innovations to realize efficient and large-scale quantum computations.

The projected ability to scale to $10^6$ qubits marks an essential step toward practical quantum computation, potentially transforming computation-heavy fields through unprecedented processing power. Future progress may involve further integration schemes across different qubit platforms, expanding the utility and adoption of this quantum architecture beyond current limitations.

This paper serves as a comprehensive guide for experienced researchers on implementing and scaling modular quantum architectures, fostering advancements that may crucially influence the trajectory of quantum technology development.