Implementation of a quantum algorithm on a nuclear magnetic resonance quantum computer

JOURNAL OF CHEMICAL PHYSICS 109:5 (1998) 1648-1653


JA Jones, M Mosca

Implementation of a quantum search algorithm on a quantum computer

NATURE 393:6683 (1998) 344-346


JA Jones, M Mosca, RH Hansen

Geometric quantum computation using nuclear magnetic resonance.

Nature 403:6772 (2000) 869-871


JA Jones, V Vedral, A Ekert, G Castagnoli


A significant development in computing has been the discovery that the computational power of quantum computers exceeds that of Turing machines. Central to the experimental realization of quantum information processing is the construction of fault-tolerant quantum logic gates. Their operation requires conditional quantum dynamics, in which one sub-system undergoes a coherent evolution that depends on the quantum state of another sub-system; in particular, the evolving sub-system may acquire a conditional phase shift. Although conventionally dynamic in origin, phase shifts can also be geometric. Conditional geometric (or 'Berry') phases depend only on the geometry of the path executed, and are therefore resilient to certain types of errors; this suggests the possibility of an intrinsically fault-tolerant way of performing quantum gate operations. Nuclear magnetic resonance techniques have already been used to demonstrate both simple quantum information processing and geometric phase shifts. Here we combine these ideas by performing a nuclear magnetic resonance experiment in which a conditional Berry phase is implemented, demonstrating a controlled phase shift gate.

Preparing High Purity Initial States for Nuclear Magnetic Resonance Quantum Computing

Physical Review Letters 93 (2004) 040501 4pp


JA Jones, MS Anwar, D Blazina, SB Duckett

Magnetic field sensing beyond the standard quantum limit using 10-spin noon states

Science 324:5931 (2009) 1166-1168


JA Jones, SD Karlen, J Fitzsimons, A Ardavan, SC Benjamin, GAD Briggs, JJL Morton


Quantum entangled states can be very delicate and easily perturbed by their external environment. This sensitivity can be harnessed in measurement technology to create a quantum sensor with a capability of outperforming conventional devices at a fundamental level. We compared the magnetic field sensitivity of a classical (unentangled) system with that of a 10-qubit entangled state, realized by nuclei in a highly symmetric molecule. We observed a 9.4-fold quantum enhancement in the sensitivity to an applied field for the entangled system and show that this spinbased approach can scale favorably as compared with approaches in which qubit loss is prevalent. This result demonstrates a method for practical quantum field sensing technology.