Spin qubits with electrically gated polyoxometalate molecules.

Spin qubits offer one of the most promising routes to the implementation of quantum computers. Very recent results in semiconductor quantum dots show that electrically-controlled gating schemes are particularly well-suited for the realization of a universal set of quantum logical gates. Scalability to a larger number of qubits, however, remains an issue for such semiconductor quantum dots. In contrast, a chemical bottom-up approach allows one to produce identical units in which localized spins represent the qubits. Molecular magnetism has produced a wide range of systems with properties that can be tailored, but so far, there have been no molecules in which the spin state can be controlled by an electrical gate. Here we propose to use the polyoxometalate [PMo12O40(VO)2]q-, where two localized spins with S = 1/2 can be coupled through the electrons of the central core. Through electrical manipulation of the molecular redox potential, the charge of the core can be changed. With this setup, two-qubit gates and qubit readout can be implemented.

[1]  D. DiVincenzo,et al.  Quantum computation with quantum dots , 1997, cond-mat/9701055.

[2]  Michael N. Leuenberger,et al.  Quantum computing in molecular magnets , 2000, Nature.

[3]  C. Hill,et al.  Introduction: Polyoxometalates-Multicomponent Molecular Vehicles To Probe Fundamental Issues and Practical Problems. , 1998, Chemical reviews.

[4]  C. Gómez‐García,et al.  Influence of metal ions on the structures of Keggin polyoxometalate-based solids : Hydrothermal syntheses, crystal structures and magnetic properties , 2006 .

[5]  Jacob M. Taylor,et al.  Coherent Manipulation of Coupled Electron Spins in Semiconductor Quantum Dots , 2005, Science.

[6]  C. R. Mayer,et al.  New organosilyl derivatives of the Dawson polyoxometalate [alpha2-P2W17O61(RSi)2O]6-: synthesis and mass spectrometric investigation. , 2004, Chemistry.

[7]  S. Blundell,et al.  Will spin-relaxation times in molecular magnets permit quantum information processing? , 2006, Physical review letters.

[8]  J. Keggin.  Structure of the Crystals of 12-Phosphotungstic Acid , 1933, Nature.

[9]  Cotunneling current through quantum dots with phonon-assisted spin-flip processes , 2005, cond-mat/0509420.

[10]  Cyrus F. Hirjibehedin,et al.  Spin Coupling in Engineered Atomic Structures , 2006, Science.

[11]  C. Hill,et al.  A Bivanadyl Capped, Highly Reduced Keggin Polyanion, [PMoV6MoVI6O40(VIVO)2]5- , 1996 .

[12]  Marco Affronte,et al.  Proposal for quantum gates in permanently coupled antiferromagnetic spin rings without need of local fields. , 2005, Physical review letters.

[13]  Jean-Luc Brédas,et al.  Single-electron transistor of a single organic molecule with access to several redox states , 2003, Nature.

[14]  K. Kern,et al.  Steering molecular organization and host–guest interactions using two-dimensional nanoporous coordination systems , 2004, Nature materials.

[15]  V. Laukhin,et al.  Coexistence of ferromagnetism and metallic conductivity in a molecule-based layered compound , 2000, Nature.

[16]  Supriyo Datta,et al.  Current-Voltage Characteristics of Self-Assembled Monolayers by Scanning Tunneling Microscopy , 1997 .

[17]  D. DiVincenzo,et al.  Coupled quantum dots as quantum gates , 1998, cond-mat/9808026.

[18]  Paul L. McEuen,et al.  Fabrication of metallic electrodes with nanometer separation by electromigration , 1999 .

[19]  Driven quantum transport on the nanoscale , 2004, cond-mat/0409251.

[20]  P. Zoller,et al.  Complete Characterization of a Quantum Process: The Two-Bit Quantum Gate , 1996, quant-ph/9611013.

[21]  D. Shultz,et al.  Semiempirical computational assessment of porphyrins as building blocks for molecule‐based magnets: spin–spin coupling in radical‐substituted metalloporphyrins , 1999 .

[22]  Signatures of molecular magnetism in single-molecule transport spectroscopy. , 2006, Nano letters.

[23]  C. Hill,et al.  A Bivanadyl Capped, Highly Reduced Keggin Polyanion, [PMo(V)(6)Mo(VI)(6)O(40)(V(IV)O)(2)](5)(-). , 1996, Inorganic chemistry.

[24]  V. Conte,et al.  Electrospray Behavior of Lacunary Keggin‐Type Polyoxotungstates [XW11O39]p− (X = Si, P): Mass Spectrometric Evidence for a Concentration‐Dependent Incorporation of an MOn+ (M = WVI, MoVI, VV) Unit into the Polyoxometalate Vacancy , 2003 .

[25]  W. Wernsdorfer,et al.  Quantum phase interference and parity effects in magnetic molecular clusters , 1999, Science.

[26]  V. Svistunov,et al.  Principles of electron tunneling spectroscopy , 1987 .

[27]  D. Barreca,et al.  Electron transport through single Mn12 molecular magnets. , 2005, Physical review letters.

[28]  Thierry Paul,et al.  Quantum computation and quantum information , 2007, Mathematical Structures in Computer Science.

[29]  Barenco,et al.  Elementary gates for quantum computation. , 1995, Physical review. A, Atomic, molecular, and optical physics.

[30]  Guanghua Li,et al.  Hydrothermal syntheses, crystal structures, and magnetic properties of inorganic-organic hybrid vanadium selenites with zero- to three-dimensional structures: (1,10-phenanthroline)(2)V(2)SeO(7), (2,2'-bipyridine)VSeO(4), (4,4'-bipyridine)V(2)Se(2)O(8), and (4,4'-bipyridine)(2)V(4)Se(3)O(15).H(2)O. , 2003, Inorganic chemistry.

[31]  J. Real,et al.  Communication between iron(II) building blocks in cooperative spin transition phenomena , 2003 .

[32]  D. Loss,et al.  Detection of single spin decoherence in a quantum dot via charge currents. , 2000, Physical review letters.

[33]  Bonnie A. Sheriff,et al.  A 160-kilobit molecular electronic memory patterned at 1011 bits per square centimetre , 2007, Nature.

[34]  W. V. D. Wiel,et al.  Electron transport through double quantum dots , 2002, cond-mat/0205350.

[35]  C. Buizert,et al.  Driven coherent oscillations of a single electron spin in a quantum dot , 2006, Nature.