Publications


Double-sided coaxial circuit QED with out-of-plane wiring

APPLIED PHYSICS LETTERS 110 (2017) ARTN 222602

J Rahamim, T Behrle, MJ Peterer, A Patterson, PA Spring, T Tsunoda, R Manenti, G Tancredi, PJ Leek


Optimal control of two qubits via a single cavity drive in circuit quantum electrodynamics

PHYSICAL REVIEW A 95 (2017) ARTN 042325

JL Allen, R Kosut, J Joo, P Leek, E Ginossar


Circuit quantum acoustodynamics with surface acoustic waves.

Nature communications 8 (2017) 975-

R Manenti, AF Kockum, A Patterson, T Behrle, J Rahamim, G Tancredi, F Nori, PJ Leek

The experimental investigation of quantum devices incorporating mechanical resonators has opened up new frontiers in the study of quantum mechanics at a macroscopic level. It has recently been shown that surface acoustic waves (SAWs) can be piezoelectrically coupled to superconducting qubits, and confined in high-quality Fabry-Perot cavities in the quantum regime. Here we present measurements of a device in which a superconducting qubit is coupled to a SAW cavity, realising a surface acoustic version of cavity quantum electrodynamics. We use measurements of the AC Stark shift between the two systems to determine the coupling strength, which is in agreement with a theoretical model. This quantum acoustodynamics architecture may be used to develop new quantum acoustic devices in which quantum information is stored in trapped on-chip acoustic wavepackets, and manipulated in ways that are impossible with purely electromagnetic signals, due to the 105 times slower mechanical waves.In this work, Manenti et al. present measurements of a device in which a tuneable transmon qubit is piezoelectrically coupled to a surface acoustic wave cavity, realising circuit quantum acoustodynamic architecture. This may be used to develop new quantum acoustic devices.


Strong Coupling of Microwave Photons to Antiferromagnetic Fluctuations in an Organic Magnet.

Physical review letters 119 (2017) 147701-

M Mergenthaler, J Liu, JJ Le Roy, N Ares, AL Thompson, L Bogani, F Luis, SJ Blundell, T Lancaster, A Ardavan, GAD Briggs, PJ Leek, EA Laird

Coupling between a crystal of di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium radicals and a superconducting microwave resonator is investigated in a circuit quantum electrodynamics (circuit QED) architecture. The crystal exhibits paramagnetic behavior above 4 K, with antiferromagnetic correlations appearing below this temperature, and we demonstrate strong coupling at base temperature. The magnetic resonance acquires a field angle dependence as the crystal is cooled down, indicating anisotropy of the exchange interactions. These results show that multispin modes in organic crystals are suitable for circuit QED, offering a platform for their coherent manipulation. They also utilize the circuit QED architecture as a way to probe spin correlations at low temperature.


Simultaneous Bistability of a Qubit and Resonator in Circuit Quantum Electrodynamics

Physical Review Letters 118 (2017)

TK Mavrogordatos, G Tancredi, M Elliott, MJ Peterer, A Patterson, J Rahamim, PJ Leek, E Ginossar, MH Szymańska


Surface acoustic wave resonators in the quantum regime

PHYSICAL REVIEW B 93 (2016) ARTN 041411(R)

R Manenti, MJ Peterer, A Nersisyan, EB Magnusson, A Patterson, PJ Leek


Surface acoustic wave devices on bulk ZnO crystals at low temperature

APPLIED PHYSICS LETTERS 106 (2015) ARTN 063509

EB Magnusson, BH Williams, R Manenti, M-S Nam, A Nersisyan, MJ Peterer, A Ardavan, PJ Leek


Coherence and decay of higher energy levels of a superconducting transmon qubit.

Physical review letters 114 (2015) 010501-

MJ Peterer, SJ Bader, X Jin, F Yan, A Kamal, TJ Gudmundsen, PJ Leek, TP Orlando, WD Oliver, S Gustavsson

We present measurements of coherence and successive decay dynamics of higher energy levels of a superconducting transmon qubit. By applying consecutive π pulses for each sequential transition frequency, we excite the qubit from the ground state up to its fourth excited level and characterize the decay and coherence of each state. We find the decay to proceed mainly sequentially, with relaxation times in excess of 20  μs for all transitions. We also provide a direct measurement of the charge dispersion of these levels by analyzing beating patterns in Ramsey fringes. The results demonstrate the feasibility of using higher levels in transmon qubits for encoding quantum information.


Applied physics. Storing quantum information in Schrödinger's cats.

Science 342 (2013) 568-569

PJ Leek


Quantum dot admittance probed at microwave frequencies with an on-chip resonator

Physical Review B - Condensed Matter and Materials Physics 86 (2012)

T Frey, PJ Leek, M Beck, J Faist, A Wallraff, K Ensslin, T Ihn, M Büttiker

We present microwave frequency measurements of the dynamic admittance of a quantum dot tunnel-coupled to a two-dimensional electron gas. The measurements are made via a high-quality 6.75 GHz on-chip resonator capacitively coupled to the dot. The resonator frequency is found to shift both down and up close to conductance resonance of the dot corresponding to a change of sign of the reactance of the system from capacitive to inductive. The observations are consistent with a scattering matrix model. The sign of the reactance depends on the detuning of the dot from conductance resonance and on the magnitude of the tunnel rate to the lead with respect to the resonator frequency. Inductive response is observed on a conductance resonance when tunnel coupling and temperature are sufficiently small compared to the resonator frequency. © 2012 American Physical Society.


Dipole Coupling of a Double Quantum Dot to a Microwave Resonator

PHYSICAL REVIEW LETTERS 108 (2012) ARTN 046807

T Frey, PJ Leek, M Beck, A Blais, T Ihn, K Ensslin, A Wallraff


Characterization of a microwave frequency resonator via a nearby quantum dot

APPLIED PHYSICS LETTERS 98 (2011) ARTN 262105

T Frey, PJ Leek, M Beck, K Ensslin, A Wallraff, T Ihn


Correlation measurements of individual microwave photons emitted from a symmetric cavity

Journal of Physics: Conference Series 264 (2011)

D Bozyigit, C Lang, L Steffen, JM Fink, C Eichler, M Baur, R Bianchetti, PJ Leek, S Filipp, A Wallraff, MP Da Silva, A Blais

Superconducting circuits have been successfully established as systems to prepare and investigate microwave light fields at the quantum level. In contrast to optical experiments where light is detected using photon counters, microwaves are usually measured with well developed linear amplifiers. This makes measurements of correlation functions - one of the important tools in optics - harder to achieve because they traditionally rely on photon counters and beam splitters. Here, we demonstrate a system where we can prepare on demand single microwave photons in a cavity and detect them at the two outputs of the cavity using linear amplifiers. Together with efficient data processing, this allows us to measure different observables of the cavity photons, including the first-order correlation function. Using these techniques we demonstrate cooling of a thermal background field in the cavity. © Published under licence by IOP Publishing Ltd.


Fabrication and heating rate study of microscopic surface electrode ion traps

NEW JOURNAL OF PHYSICS 13 (2011) ARTN 013032

N Daniilidis, S Narayanan, SA Moeller, R Clark, TE Lee, PJ Leek, A Wallraff, S Schulz, F Schmidt-Kaler, H Haeffner


Resolving Vacuum Fluctuations in an Electrical Circuit by Measuring the Lamb Shift

SCIENCE 322 (2008) 1357-1360

A Fragner, M Goeppl, JM Fink, M Baur, R Bianchetti, PJ Leek, A Blais, A Wallraff


Adiabatic charge pumping in carbon nanotube quantum dots

PHYSICAL REVIEW LETTERS 101 (2008) ARTN 126803

MR Buitelaar, V Kashcheyevs, PJ Leek, VI Talyanskii, CG Smith, D Anderson, GAC Jones, J Wei, DH Cobden


Climbing the Jaynes-Cummings ladder and observing its root n nonlinearity in a cavity QED system

NATURE 454 (2008) 315-318

JM Fink, M Goeppl, M Baur, R Bianchetti, PJ Leek, A Blais, A Wallraff


Observation of Berry's phase in a solid-state qubit

SCIENCE 318 (2007) 1889-1892

PJ Leek, JM Fink, A Blais, R Bianchetti, M Goeppl, JM Gambetta, DI Schuster, L Frunzio, RJ Schoelkopf, A Wallraff


Charge pumping and current quantization in surface acoustic-wave-driven carbon nanotube devices

SEMICONDUCTOR SCIENCE AND TECHNOLOGY 21 (2006) S69-S77

MR Buitelaar, PJ Leek, VI Talyanskii, CG Smith, D Anderson, GAC Jones, J Wei, DH Cobden


Charge pumping in carbon nanotubes

PHYSICAL REVIEW LETTERS 95 (2005) ARTN 256802

PJ Leek, MR Buitelaar, VI Talyanskii, CG Smith, D Anderson, GAC Jones, J Wei, DH Cobden

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