Quantum spin dynamics

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Electron paramagnetic resonance investigation of purified catalyst-free single-walled carbon nanotubes

ACS Nano 4:12 (2010) 7708-7716

Authors:

M Zaka, Y Ito, H Wang, W Yan, A Robertson, YA Wu, MH Rümmeli, D Staunton, T Hashimoto, JJL Morton, A Ardavan, GAD Briggs, JH Warner

Abstract:

Electron paramagnetic resonance of single-walled carbon nanotubes (SWCNTs) has been bedevilled by the presence of paramagnetic impurities. To address this, SWCNTs produced by laser ablation with a nonmagnetic PtRhRe catalyst were purified through a multiple step centrifugation process in order to remove amorphous carbon and catalyst impurities. Centrifugation of a SWCNT solution resulted in sedimentation of carbon nanotube bundles containing clusters of catalyst particles, while isolated nanotubes with reduced catalyst particle content remained in the supernatant. Further ultracentrifugation resulted in highly purified SWCNT samples with a narrow diameter distribution and almost no detectable catalyst particles. Electron paramagnetic resonance (EPR) signals were detected only for samples which contained catalyst particles, with the ultracentrifuged SWCNTs showing no EPR signal at X-band (9.4 GHz) and fields < 0.4 T. © 2010 American Chemical Society.
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Quantum interference between photo-excited states in a solid-state mott insulator

Optics InfoBase Conference Papers (2010)

Authors:

S Wall, D Brida, SR Clark, HP Ehrke, D Jaksch, A Ardavan, S Bonora, H Uemura, Y Takahashi, T Hasegawa, H Okamoto, G Cerullo, A Cavalleri

Abstract:

By exciting with sub-10-fs 1.6-μm pulses the quasi-one-dimensional Mott insulator ETF2TCNQ, we observe prompt collapse of the Mott gap modulated by 24-THz oscillations of the gap, which are assigned to quantum interference between holon-doublon excitations. © 2010 Optical Society of America.

Coherent state transfer between an electron- and nuclear spin in 15N@C60

(2010)

Authors:

Richard M Brown, Alexei M Tyryshkin, Kyriakos Porfyrakis, Erik M Gauger, Brendon W Lovett, Arzhang Ardavan, SA Lyon, G Andrew D Briggs, John JL Morton
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Quantum interference between photo-excited states in a solid-state Mott insulator

Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference: 2010 Laser Science to Photonic Applications, CLEO/QELS 2010 (2010)

Authors:

S Wall, D Brida, SR Clark, HP Ehrke, D Jaksch, A Ardavan, S Bonora, H Uemura, Y Takahashi, T Hasegawa, H Okamoto, G Cerullo, A Cavalleri

Abstract:

By exciting with sub-10-fs 1.6-μm pulses the quasi-one-dimensional Mott insulator ETF2TCNQ, we observe prompt collapse of the Mott gap modulated by 24-THz oscillations of the gap, which are assigned to quantum interference between holon-doublon excitations. © 2010 Optical Society of America.
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Storage of multiple coherent microwave excitations in an electron spin ensemble.

Phys Rev Lett 105:14 (2010) 140503

Authors:

Hua Wu, Richard E George, Janus H Wesenberg, Klaus Mølmer, David I Schuster, Robert J Schoelkopf, Kohei M Itoh, Arzhang Ardavan, John JL Morton, G Andrew D Briggs

Abstract:

Strong coupling between a microwave photon and electron spins, which could enable a long-lived quantum memory element for superconducting qubits, is possible using a large ensemble of spins. This represents an inefficient use of resources unless multiple photons, or qubits, can be orthogonally stored and retrieved. Here we employ holographic techniques to realize a coherent memory using a pulsed magnetic field gradient and demonstrate the storage and retrieval of up to 100 weak 10 GHz coherent excitations in collective states of an electron spin ensemble. We further show that such collective excitations in the electron spin can then be stored in nuclear spin states, which offer coherence times in excess of seconds.
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