Decoherence and quantum computing

Jeff Heckey, Shruti R. Patil, Ali Javadi-Abhari +6 more

Quantum computing (QC) offers huge promise to accelerate a range of computationally intensive benchmarks. Quantum computing is limited, however, by the challenges of decoherence: i.e., a quantum state can only be maintained for short windows of time before it decoheres. While quantum error correction codes can protect against decoherence, fast execution time is the best defense against decoherence, so efficient architectures and effective scheduling algorithms are necessary. This paper proposes the Multi-SIMD QC architecture and then proposes and evaluates effective schedulers to map benchmark descriptions onto Multi-SIMD architectures. The Multi-SIMD model consists of a small number of SIMD regions, each of which may support operations on up to thousands of qubits per cycle.

Vladimir Privman A

M. Tei, Yoichi Mizuno, Yoshinori Manmoto +2 more

Abstract Recently, quantum algorithms have been realized on a quantum computer by using a nuclear magnetic resonance technique. The nuclear magnetic resonance quantum computer (NMR‐QC) consists of nuclear spins of molecules that are coupled by J‐coupling to each other and the nuclear spins take a role of quantum bits (qubits). In performing quantum algorithms on NMR‐QC, the decoherence effects are a key problem. We studied the decoherence effects in the four‐qubit NMR‐QC using the fluorine nuclear spins of tetrafluoropyridine molecules. The nitrogen nuclear spin in the tetrafluoropyridine molecule increases the transverse relaxation rate of nearby fluorine nuclear spins about 10 times because of its quadrupole moment. In this study we evaluated the decoherence effects in the NMR‐QC by utilizing controlled‐not quantum gates. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003

Mark Tame, Mauro Paternostro, M S Kim

We introduce a novel scheme for one-way quantum computing (QC) based on the use of information encoded qubits in an effective cluster state resource. With the correct encoding structure, we show that it is possible to protect the entangled resource from phase damping decoherence, where the effective cluster state can be described as residing in a decoherence-free subspace (DFS) of its supporting quantum system. One-way QC then requires either single or two-qubit adaptive measurements. As an example where this proposal can be realized, we describe an optical lattice set-up where the scheme provides robust quantum information processing. We also outline how one can adapt the model to provide protection from other types of decoherence.

Tarun Sanghi, Jha, RM