Control of Quantum Evolution and Josephson Junction Circuits

Dissertation

Antti Niskanen

Research output: ThesisDissertationCollection of Articles

Abstract

Ever since Peter Shor's ground-breaking discovery in 1994 of an algorithm capable of factoring large integers on a quantum-mechanical computer exponentially faster than using any known classical method, research on quantum computing has boomed. Quantum information - a unique mixture of computer science, physics and mathematics - has developed into a new branch of information theory. On the experimental side, physicists from many different disciplines including atomic, solid-state and low-temperature physics, as well as optics, are striving today towards a practical quantum computer. All the candidate quantum bit (qubit) technologies have one thing in common: They rely on the controlled time-evolution of a closed quantum system, a seemingly paradoxical task. In this Thesis the temporal control of quantum systems is studied. The topics included can be divided into two according to the type of temporal evolution; geometrical or dynamical. Geometrical realization-independent methods for quantum computing are studied first. Then the study is extended into dynamical quantum computing and the so-called Josephson charge-qubit register is considered as a test bench. Finally, a spin-off application of the geometrical evolution of a Josephson junction system is studied, i.e. Cooper pair pumping. A novel Cooper pair pump, the Cooper pair "sluice", is introduced. The work on quantum computing reported in this Thesis is theoretical while the Cooper pair "sluice" is studied both theoretically and experimentally. Numerical simulations, both sequential and parallel, are used extensively throughout the Thesis. The experiments were carried out under cryogenic mK conditions and the sample fabrication was done using e-beam nanolithography. Because the execution time of a quantum algorithm is always limited by the inevitable process of decoherence, it is important to utilize any measure available for accelerating quantum computations. It is found that practical quantum algorithms could greatly benefit from classical computer-aided optimization. Moreover, it is found that even a modest demonstrator of a full quantum algorithm using Josephson charge qubits is just barely realizable within present-day coherence times. However, the experimental part of this Thesis shows clear evidence of the functioning of the "sluice". While the worldwide effort of improving the coherence properties of qubits is underway, the "sluice" could well find practical use, e.g., in metrology in the foreseeable future.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
Award date26 Nov 2004
Place of PublicationEspoo
Publisher
Print ISBNs951-38-6420-0
Electronic ISBNs951-38-6421-9
Publication statusPublished - 2004
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

quantum computation
Josephson junctions
theses
low temperature physics
quantum computers
information theory
registers
mathematics
metrology
seats
integers
cryogenics
pumping
optics
pumps
solid state
fabrication
physics
optimization
simulation

Keywords

  • quantum systems
  • quantum mechanics
  • quantum computing
  • quantum algorithms
  • Cooper pair pumping
  • Josephson junction

Cite this

Niskanen, A. (2004). Control of Quantum Evolution and Josephson Junction Circuits: Dissertation. Espoo: VTT Technical Research Centre of Finland.
Niskanen, Antti. / Control of Quantum Evolution and Josephson Junction Circuits : Dissertation. Espoo : VTT Technical Research Centre of Finland, 2004. 111 p.
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Niskanen, A 2004, 'Control of Quantum Evolution and Josephson Junction Circuits: Dissertation', Doctor Degree, Aalto University, Espoo.

Control of Quantum Evolution and Josephson Junction Circuits : Dissertation. / Niskanen, Antti.

Espoo : VTT Technical Research Centre of Finland, 2004. 111 p.

Research output: ThesisDissertationCollection of Articles

TY - THES

T1 - Control of Quantum Evolution and Josephson Junction Circuits

T2 - Dissertation

AU - Niskanen, Antti

PY - 2004

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N2 - Ever since Peter Shor's ground-breaking discovery in 1994 of an algorithm capable of factoring large integers on a quantum-mechanical computer exponentially faster than using any known classical method, research on quantum computing has boomed. Quantum information - a unique mixture of computer science, physics and mathematics - has developed into a new branch of information theory. On the experimental side, physicists from many different disciplines including atomic, solid-state and low-temperature physics, as well as optics, are striving today towards a practical quantum computer. All the candidate quantum bit (qubit) technologies have one thing in common: They rely on the controlled time-evolution of a closed quantum system, a seemingly paradoxical task. In this Thesis the temporal control of quantum systems is studied. The topics included can be divided into two according to the type of temporal evolution; geometrical or dynamical. Geometrical realization-independent methods for quantum computing are studied first. Then the study is extended into dynamical quantum computing and the so-called Josephson charge-qubit register is considered as a test bench. Finally, a spin-off application of the geometrical evolution of a Josephson junction system is studied, i.e. Cooper pair pumping. A novel Cooper pair pump, the Cooper pair "sluice", is introduced. The work on quantum computing reported in this Thesis is theoretical while the Cooper pair "sluice" is studied both theoretically and experimentally. Numerical simulations, both sequential and parallel, are used extensively throughout the Thesis. The experiments were carried out under cryogenic mK conditions and the sample fabrication was done using e-beam nanolithography. Because the execution time of a quantum algorithm is always limited by the inevitable process of decoherence, it is important to utilize any measure available for accelerating quantum computations. It is found that practical quantum algorithms could greatly benefit from classical computer-aided optimization. Moreover, it is found that even a modest demonstrator of a full quantum algorithm using Josephson charge qubits is just barely realizable within present-day coherence times. However, the experimental part of this Thesis shows clear evidence of the functioning of the "sluice". While the worldwide effort of improving the coherence properties of qubits is underway, the "sluice" could well find practical use, e.g., in metrology in the foreseeable future.

AB - Ever since Peter Shor's ground-breaking discovery in 1994 of an algorithm capable of factoring large integers on a quantum-mechanical computer exponentially faster than using any known classical method, research on quantum computing has boomed. Quantum information - a unique mixture of computer science, physics and mathematics - has developed into a new branch of information theory. On the experimental side, physicists from many different disciplines including atomic, solid-state and low-temperature physics, as well as optics, are striving today towards a practical quantum computer. All the candidate quantum bit (qubit) technologies have one thing in common: They rely on the controlled time-evolution of a closed quantum system, a seemingly paradoxical task. In this Thesis the temporal control of quantum systems is studied. The topics included can be divided into two according to the type of temporal evolution; geometrical or dynamical. Geometrical realization-independent methods for quantum computing are studied first. Then the study is extended into dynamical quantum computing and the so-called Josephson charge-qubit register is considered as a test bench. Finally, a spin-off application of the geometrical evolution of a Josephson junction system is studied, i.e. Cooper pair pumping. A novel Cooper pair pump, the Cooper pair "sluice", is introduced. The work on quantum computing reported in this Thesis is theoretical while the Cooper pair "sluice" is studied both theoretically and experimentally. Numerical simulations, both sequential and parallel, are used extensively throughout the Thesis. The experiments were carried out under cryogenic mK conditions and the sample fabrication was done using e-beam nanolithography. Because the execution time of a quantum algorithm is always limited by the inevitable process of decoherence, it is important to utilize any measure available for accelerating quantum computations. It is found that practical quantum algorithms could greatly benefit from classical computer-aided optimization. Moreover, it is found that even a modest demonstrator of a full quantum algorithm using Josephson charge qubits is just barely realizable within present-day coherence times. However, the experimental part of this Thesis shows clear evidence of the functioning of the "sluice". While the worldwide effort of improving the coherence properties of qubits is underway, the "sluice" could well find practical use, e.g., in metrology in the foreseeable future.

KW - quantum systems

KW - quantum mechanics

KW - quantum computing

KW - quantum algorithms

KW - Cooper pair pumping

KW - Josephson junction

M3 - Dissertation

SN - 951-38-6420-0

T3 - VTT Publications

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Niskanen A. Control of Quantum Evolution and Josephson Junction Circuits: Dissertation. Espoo: VTT Technical Research Centre of Finland, 2004. 111 p.