Preparing high purity initial states for nuclear magnetic resonance quantum computing

Abstract

Here we demonstrate how para-hydrogen can be used to prepare a two-spin system in an almost pure state which is suitable for implementing nuclear magnetic resonance (NMR) quantum computation. A 12ns laser pulse is used to initiate a chemical reaction involving pure para-hydrogn (the nuclear spin singlet of H2). The product, formed on the microsecond timescale, contains a hydrogen derived two-spin system with an effective spin-state purity of 0.916. To achieve a comparable result by direct cooling would require an unmanageable (in the liquid state) effective spin temperature of 6.4mK or an impractical magnetic field of 0.45MT at room temperature. The resulting spin state has an entanglement of formation of 0.822 and cannot be described by local hidden variable models.

4 pages including 2 figures. Changes from v.3 at request of referees. Now in press at Physical Review Letters

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• NMR Analog of Bell's Inequalities Violation Test
• Average Fidelity in n-Qubit systems
• Implementation of NMR quantum computation with para-hydrogen derived high purity quantum states
• Practical Implementations of Twirl Operations
• Entanglement and Symmetry: A Case Study in Superselection Rules, Reference Frames, and Beyond
• Thermal Equilibrium as an Initial State for Quantum Computation by NMR
• Diversity of Parahydrogen-Induced Hyperpolarization Effects in Chemistry
• Controlling NMR spin systems for quantum computation
• Transforming pure and mixed states using an NMR quantum homogeniser
• Fault Models for Quantum Mechanical Switching Networks
• Bounds on the entanglability of thermal states in liquid-state nuclear magnetic resonance
• Witnesses of non-classicality for simulated hybrid quantum systems
• Single qubit gates by selective excitation with Jump and Return sequences
• Numerical Analysis of Boosting Scheme for Scalable NMR Quantum Computation
• Polarization Requirements for Ensemble Implementations of Quantum Algorithms with a Single Bit Output
• Teleportation protocol with non-ideal conditional local operations
• Experimental Heat-Bath Cooling of Spins
• Sharing Polarization within Quantum Subspaces
• Statistical comparison of ensemble implementations of Grover's search algorithm to classical sequential searches
• Attainable entanglement of unitary transformed thermal states in liquid-state nuclear magnetic resonance with the chemical shift