arXiv subjects

I. Mahboob

Publications and source records attributed to I. Mahboob.

6 recordsLinked to original sources

arXiv2022

A three-dimensional Josephson parametric amplifier

A Josephson parametric amplifier (JPA) is executed in a three-dimensional (3D) microwave cavity by coupling it to a superconducting quantum interference device (SQUID) that is embedded in a two-dimensional resonator. The JPA is activated in a three-wave mixing configuration by injecting ac magnetic flux, at twice the 3D cavity frequency, into the SQUID. An 8.3 GHz cavity is measured in a non-degenerate phase-insensitive configuration which yields gains in excess of 40 dB, where a 20 dB gain results in an operational bandwidth of 0.4 MHz, a 1 dB compression point of -115 dBm with half a quantum of added noise.

quant-ph↗

arXiv2018

Virtual exceptional points in an electromechanical system

Non-Hermitian Hamiltonians can give rise to exceptional points (EPs) which have been extensively explored with nominally identical coupled resonators. Here a non-Hermitian electromechanical system is developed which hosts vibration modes that differ massively in their spatial profile, frequency and even the sign of their dissipation. An optomechanical-like parametric modulation is employed to dynamically couple 2 of these disparate modes and in the appropriate parameter regime their imaginary eigenvalues coalesce whilst their normal modes split. The presence of this virtual EP is confirmed via numerical simulations of the coupled equations of motions describing the dynamics of this non-degenerate system. These results suggest that virtual EPs can be accessed in systems composed from highly mismatched resonators whilst still maintaining access to the non-trivial phenomenon in their proximity, as recently demonstrated for topological operations, thus enabling non-Hermitian singularities to be more widely exploited with realistic physical systems.

cond-mat.mes-hall↗

arXiv2015

An electromechanical Ising machine

Solving intractable mathematical problems in simulators composed of atoms, ions, photons or electrons has recently emerged as a subject of intense interest. Here we extend this concept to phonons that are localised in spectrally pure resonances in an electromechanical system which enables their interactions to be exquisitely fashioned via electrical means. We harness this platform to emulate the Ising Hamiltonian whose spin 1/2 particles are replicated by the phase bistable vibrations from a parametric resonance where multiple resonances play the role of a spin bath. The coupling between the mechanical pseudo spins is created by generating thermomechanical two-mode squeezed states which impart correlations between resonances that can imitate a ferromagnetic, random or an anti-ferromagnetic state on demand. These results suggest an electromechanical simulator for the Ising Hamiltonian could be built with a large number of spins with multiple degrees of coupling, a task that would overwhelm a conventional computer.

cond-mat.mes-hall↗

arXiv2014

Two-mode squeezing in an electromechanical resonator

The widespread availability of quantum entanglement with photons, in the guise of two-mode squeezed states, can be attributed to the phenomenon of parametric down-conversion. A reinterpretation of this effect with macroscopic mechanical objects can offer a route towards a purely mechanical entanglement and the unique possibility of probing the quantum mechanical nature of our everyday classical world. In spite of this prospect, mechanical two-mode squeezed states have remained elusive due to the inability to recreate the nonlinear interaction at the heart of this phenomenon in the mechanical domain. To address this we have developed a parametric down-converter, in a mechanical resonator integrated with electrical functionality, which enables mechanical nonlinearities to be dynamically engineered to emulate the parametric down-conversion interaction. In this configuration, phonons are simultaneously generated in pairs in two macroscopic vibration modes which results in the amplification of their motion. In parallel, mechanical two-mode squeezed states are also created which exhibit fluctuations far below the thermal level of their constituent modes as well as harbouring correlations between the modes that become almost perfect as their amplification is increased. This remarkable observation of correlations between two massive phonon ensembles paves the way towards an entangled macroscopic mechanical system at the single phonon level.

cond-mat.mes-hall↗

arXiv2010

Tunable backaction of a dc SQUID on an integrated micromechanical resonator

We have measured the backaction of a dc superconducting quantum interference device (SQUID) position detector on an integrated 1 MHz flexural resonator. The frequency and quality factor of the micromechanical resonator can be tuned with bias current and applied magnetic flux. The backaction is caused by the Lorentz force due to the change in circulating current when the resonator displaces. The experimental features are reproduced by numerical calculations using the resistively and capacitively shunted junction (RCSJ) model.

cond-mat.mes-hall↗

arXiv2007

Electron spin manipulation and resonator readout in a double quantum dot nano-electromechanical system

Magnetically coupling a nano-mechanical resonator to a double quantum dot confining two electrons can enable the manipulation of a single electron spin and the readout of the resonator's natural frequency. When the Larmor frequency matches the resonator frequency, the electron spin in one of the dots can be selectively flipped by the magnetised resonator. By simultaneously measuring the charge state of the two-electron double quantum dots, this transition can be detected thus enabling the natural frequency of the mechanical resonator to be determined.

cond-mat.mes-hall↗