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A High Quality Factor Carbon Nanotube Mechanical Resonator at 39 GHz

Mon, 2013-02-11 18:46 - Daniel Rudolph
Date: 
2011-11-23
Author(s): 

E. A. Laird, F. Pei, W. Tang, G. A. Steele and L. P. Kouwenhoven

Reference: 

Nano Lett. 12, 193 (2012)

URL: 

http://dx.doi.org/10.1021/nl203279v

We measure the mechanical resonances of an as-grown suspended carbon nanotube, detected via electrical mixing in the device. A sequence of modes extending to 39 GHz is observed with a quality factor of 35 000 in the highest mode. This unprecedentedly high combination corresponds to a thermal excited state probability below 10–8 and a relaxation time of 140 ns with microsecond relaxation times for lower modes. The effect of electron tunneling on the mechanical resonance is found to depend on frequency as the tunneling time becomes comparable to the vibration period.

Signatures of Majorana Fermions in Hybrid Superconductor-Semiconductor Nanowire Devices

Mon, 2013-02-11 18:43 - Daniel Rudolph
Date: 
2012-04-12
Author(s): 

V. Mourik, K. Zuo, S. M. Frolov, S. R. Plissard, E. P. A. M. Bakkers and L. P. Kouwenhoven

Reference: 

Science 336, 1003 (2012)

URL: 

http://www.sciencemag.org/content/336/6084/1003.full

Majorana fermions are particles identical to their own antiparticles. They have been theoretically predicted to exist in topological superconductors. Here, we report electrical measurements on indium antimonide nanowires contacted with one normal (gold) and one superconducting (niobium titanium nitride) electrode. Gate voltages vary electron density and define a tunnel barrier between normal and superconducting contacts. In the presence of magnetic fields on the order of 100 millitesla, we observe bound, midgap states at zero bias voltage.

Spectroscopy of Spin-Orbit Quantum Bits in Indium Antimonide Nanowires

Mon, 2013-02-11 18:41 - Daniel Rudolph
Date: 
2012-04-19
Author(s): 

S. Nadj-Perge, V. S. Pribiag, J. W. G. van den Berg, K. Zuo, S. R. Plissard, E. P. A. M. Bakkers, S. M. Frolov and L. P. Kouwenhoven

Reference: 

Phys. Rev. Lett. 108, 166801 (2012)

URL: 

http://link.aps.org/doi/10.1103/PhysRevLett.108.166801

From InSb Nanowires to Nanocubes: Looking for the Sweet Spot

Mon, 2013-02-11 18:40 - Daniel Rudolph
Date: 
2012-02-24
Author(s): 

S. R. Plissard, D. R. Slapak, M. A. Verheijen, M. Hocevar, G. W. G. Immink, I. van Weperen, S. Nadj-Perge, S. M. Frolov, L. P. Kouwenhoven and E. P. A. M. Bakkers

Reference: 

Nano Lett. 12, 1794 (2012)

URL: 

http://dx.doi.org/10.1021/nl203846g

High aspect ratios are highly desired to fully exploit the one-dimensional properties of indium antimonide nanowires. Here we systematically investigate the growth mechanisms and find parameters leading to long and thin nanowires.

Valley–spin blockade and spin resonance in carbon nanotubes

Mon, 2013-02-11 18:37 - Daniel Rudolph
Date: 
2012-09-23
Author(s): 

F. Pei, E. A. Laird, G. A. Steele and L. P. Kouwenhoven

Reference: 

Nature Nanotechnology 7, 630 (2012)

URL: 

http://www.nature.com/nnano/journal/v7/n10/full/nnano.2012.160.html

The manipulation and readout of spin qubits in quantum dots have been successfully achieved using Pauli blockade, which forbids transitions between spin–triplet and spin–singlet states. Compared with spin qubits realized in III–V materials, group IV materials such as silicon and carbon are attractive for this application because of their low decoherence rates (nuclei with zero spins).

Selective darkening of degenerate transitions for implementing quantum controlled-NOT gates

Mon, 2013-02-11 18:32 - Daniel Rudolph
Date: 
2012-07-17
Author(s): 

P. C. de Groot, S. Ashhab, A. Lupaşcu, L. DiCarlo, F. Nori, C. J. P. M. Harmans and J. E. Mooij

Reference: 

New J. Phys. 14, 073038 (2012)

URL: 

http://dx.doi.org/10.1088/1367-2630/14/7/073038

Initialization by Measurement of a Superconducting Quantum Bit Circuit

Mon, 2013-02-11 18:29 - Daniel Rudolph
Date: 
2012-08-03
Author(s): 

D. Ristè, J. G. van Leeuwen, H.-S. Ku, K. W. Lehnert, and L. DiCarlo

Reference: 

Phys. Rev. Lett. 109, 050507 (2012)

URL: 

http://link.aps.org/doi/10.1103/PhysRevLett.109.050507

We demonstrate initialization by joint measurement of two transmon qubits in 3D circuit quantum electrodynamics. Homodyne detection of cavity transmission is enhanced by Josephson parametric amplification to discriminate the two-qubit ground state from single-qubit excitations nondestructively and with 98.1% fidelity. Measurement and postselection of a steady-state mixture with 4.7% residual excitation per qubit achieve 98.8% fidelity to the ground state, thus outperforming passive initialization.

 

Feedback Control of a Solid-State Qubit Using High-Fidelity Projective Measurement

Mon, 2013-02-11 18:25 - Daniel Rudolph
Date: 
2012-12-10
Author(s): 

D. Ristè, C. C. Bultink, K. W. Lehnert, and L. DiCarlo

Reference: 

Phys. Rev. Lett. 109, 240502 (2012)

URL: 

http://link.aps.org/doi/10.1103/PhysRevLett.109.240502

We demonstrate feedback control of a superconducting transmon qubit using discrete, projective measurement and conditional coherent driving. Feedback realizes a fast and deterministic qubit reset to a target state with 2.4% error averaged over input superposition states, and allows concatenating experiments more than 10 times faster than by passive initialization. This closed-loop qubit control is necessary for measurement-based protocols such as quantum error correction and teleportation.

 

Millisecond charge-parity fluctuations and induced decoherence in a superconducting qubit

Mon, 2013-02-11 18:23 - Daniel Rudolph
Date: 
2012-12-21
Author(s): 

D. Ristè, C. C. Bultink, M. J. Tiggelman, R. N. Schouten, K. W. Lehnert, L. DiCarlo

Reference: 

arXiv:1212.5459 [cond-mat.mes-hall]

URL: 

http://arxiv.org/abs/1212.5459

Quasiparticle excitations adversely affect the performance of superconducting devices in a wide range of applications. They limit the sensitivity of photon detectors in astronomy, the accuracy of current sources in metrology, the cooling power of micro-refrigerators, and could break the topological protection of Majorana qubits. In superconducting circuits for quantum information processing, tunneling of quasiparticles across Josephson junctions constitutes a decoherence mechanism.

Fast Path and Polarization Manipulation of Telecom Wavelength Single Photons in Lithium Niobate Waveguide Devices

Mon, 2013-02-11 18:12 - Daniel Rudolph
Date: 
2012-01-31
Author(s): 

D. Bonneau, M. Lobino, P. Jiang, C. M. Natarajan, M. G. Tanner, R. H. Hadfield, S. N. Dorenbos, V. Zwiller, M. G. Thompson, and J. L. O’Brien

Reference: 

Phys. Rev. Lett. 108, 053601 (2012)

URL: 

http://link.aps.org/doi/10.1103/PhysRevLett.108.053601

We demonstrate fast polarization and path control of photons at 1550 nm in lithium niobate waveguide devices using the electro-optic effect. We show heralded single photon state engineering, quantum interference, fast state preparation of two entangled photons, and feedback control of quantum interference. These results point the way to a single platform that will enable the integration of nonlinear single photon sources and fast reconfigurable circuits for future photonic quantum information science and technology.

 

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