Biomedical subjects

WS Warren

Publications and source records attributed to WS Warren.

9 recordsLinked to original sources

PubMed2000

Automatic quantum error correction

Criteria are given by which dissipative evolution in the weak coupling limit can transfer populations and coherences between quantum subspaces, without a loss of coherence. The result is a form of quantum error correction implemented by the joint evolution of a system with a cold bath. It requires no external intervention and, in principle, no ancilla. An example of such a system, consisting of three dipole ordered spin 1/2 particles in a resonator, is given. The qubit, or the triple quantum coherence of the spins, is protected against all spin-flip errors.

Journal Article↗

PubMed1998

Intermolecular zero-quantum coherences of multi-component spin systems in solution NMR

Intermolecular zero-quantum coherences (iZQC) induced by the dipolar demagnetizing field can give both P- and N-type cross peaks. This paper shows that the relative intensities of the two types of iZQC peaks follow a simple relation, tan2 (theta/2), from both the quantum (spin density matrix) and classical (modified Bloch equation) calculations. The experimental data and numerical simulations agree well with the prediction. In addition, higher-order iZQCs are experimentally examined for the first time and are explained by the quantum picture in which dipolar couplings convert four-spin operators into observable magnetization. Copyright 1998 Academic Press.

Journal Article↗

PubMed1995