Quantum noise correlations and amplifiers in mesoscopic systems

Pasi Lähteenmäki

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

This thesis work deals with a range of superconducting devices operated near the fundamental performance limits set by quantum mechanics along with the nature of quantum vacuum itself when perturbed by such devices. These devices are operated in a dilution refrigerator cooled down to sub-Kelvin temperatures. Low temperature is absolutely essential for quantum behavior of these devices and the minimal inherent noise contribution. Biased, selectively damped superconducting tunnel junction, (also known as the Josephson junction) displaying negative differential resistance, was employed to construct a device capable of amplifying weak microwave signal reflections from it. This device can be operated near the intrinsic precision limits set by the Heisenberg's uncertainty principle. Arrays of Superconducting Quantum Interference Devices (SQUIDs), operated below the critical current, can be used for metamaterial resonators whose resonant frequency can be quickly modulated by magnetic flux. These devices are operated as parametric amplifiers and they are capable of amplifying weak microwave signals near the quantum limit of noise. But more importantly, they are capable of perturbing the vacuum itself, which creates correlated photon pairs seeded by vacuum fluctuations. This effect is known as the dynamical Casimir effect (DCE) and is demonstrated in this thesis work by using power and correlation measurements at microwave frequencies. Furthermore, investigations on the DCE have been extended using a double modulation scheme yielding vacuum-induced coherence and tripartite correlations. Nanocarbon devices have also been studied in this thesis, in particular a wideband low noise nanotube electrometer constructed from a nanotube with proximity induced superconductivity. This device has certain unique benefits when operated in a microwave environment which are discussed in the thesis. Another nanocarbon device, a double quantum dot constructed from graphene and superconducting leads has been used to demonstrate Cooper-pair splitting. This device operates as a tunable source of entangled electrons.
Translated title of the contributionQuantum noise correlations and amplifiers in mesoscopic systems
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Hakonen, Pertti, Supervising Professor
Publisher
Print ISBNs978-952-60-6627-1
Electronic ISBNs978-952-60-6628-8
Publication statusPublished - 2016
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • superconductivity
  • nanoelectronics
  • parametric amplifier
  • dynamical Casimir effect
  • metamaterials
  • Josephson junction
  • SQUID
  • quantum mechanics
  • carbon nanotube
  • graphene
  • Cooper-pair

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