A general purpose architectural layout for arbitrary quantum computations
Tzvetan S. Metodi, Darshan Thaker, Andrew W. Cross, Frederic T. Chong, Isaac L. Chuang · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2005
Exploiting recent advances in quantum trapped-ion technologies, we propose a scalable, fault-tolerant quantum computing architecture that overcomes the fundamental challenges of building a full-scale quantum computer and leaves the fabrication a daunting but primarily an engineering concern. Using a hierarchical array-based design and a quantum teleportation communication protocol, we are able to overcome the primary scalability challenges of reliability, communication, and quantum resource distribution. In particular, we present a reconfigurable quantum circuit substrate, or "quantum FPGA'' (qFPGA) which allows efficient implementation of universal quantum gates and error correction. We use this qFPGA as a basic building block for an array structure that scalably provides communication channels and quantum resource distribution. We exploit a hierarchical combination of ballistic transport of data ions and quantum teleportation to reduce the cost of reliable communication from exponential to polynomial in distance. By using a set of simulation tools we are able to evaluate a hypothetical design of a future general purpose quantum computer and describe the execution of a fault-tolerant Toffoli gate construction. Without considering classical control constraints and assuming best-possible ion-trap parameters our computer consists of level 2 encoded qubits with the Steane \ecc code tightly connected by the teleportation interconnect, and capable of executing a fault-tolerant Toffoli gate in roughly 2.3 seconds. This translates to factoring a 128-bit number in slightly over 40 hours in circuits dominated by Toffoli gates.