title: Macroscopic quantum phenomena

authors: Munro, William John

subjects: Quantum theory

abstract: This thesis consists of two parts. Although both are concerned with macroscopic quantum phenomena, I choose to present the two parts quite separately.  

Macroscopic Quantum Phenomena: Tests of Quantum Mechanics 

The correctness of quantum mechanics has been verified in numerous situations. A particularly strong test of quantum mechanics was suggested by Bell, who showed that the predictions of all classical theories, based as they are on the assumptions of local realism, contradict those of quantum mechanics. Later work by Greenberger, Horne, and Zeilinger showed that the GHZ phenomena also contradicts all classical theories. Experimental tests of Bells inequality performed to date support quantum mechanics (No experimental test of the GHZ phenomenon has yet been attempted). However, such tests have been so far restricted to microscopic systems in the sense that one particle is at a detector at a time.  
Our interest here in the first part of this thesis is in tests of quantum mechanics against local realistic theories in macroscopic or mesoscopic systems where there is a significant number of particles incident on each analyser. The states considered in the first two chapters are not simple quantum superpositions of macroscopically distinct states, but we nevertheless show how one can obtain tests of quantum mechanics in situations involving large numbers of particles. A more elementary macroscopic quantum state, and one in which the deviation from classical interpretations is striking, is the Schrodinger Cat state considered by Schrodinger in his famous "Schrodinger Cat" paradox. In Chapter Three we consider a scheme for generating such a state. 

The Quantum Brownian Motion Master Equation 

The second section of this thesis involves an examination of various aspects of the Quantum Brownian Motion Master Equation. We begin with a discussion of the recent problem occurring from the study of the quantum Brownian motion (QBM) master equation, which can occur because the QBM master equation is not of the Lindblad form. We examine two specific examples, namely the damped free particle and the two level atom. More specifically, in the case of the evolution of a free particle, we show that the equation of motion for the Wigner function (which is exactly the same as the Fokker-Planck equation for classical Brownian motion) gives unphysical results if the initial position distribution is well localised. In the case of the two level atom we show that unphysical results can also occur even in the steady state. 
The last chapter of the thesis involves using the quantum Brownian motion master equation to estimate the rate of diagonalisation of the off diagonal elements of a Fermion system. These elements contain the "quantum information" and hence knowledge of how long they exist can determine the type of model required to describe the semiconductor medium. Using a very simplistic approach we can show that there are two main time scales present and for normal parameters one of these is very small. If we neglect electron-electron scattering we can show that the the many electron system solution is simply a product of the one electron solutions.

text: Macroscopic quantum phenomena This thesis consists of two parts. Although both are concerned with macroscopic quantum phenomena, I choose to present the two parts quite separately.  

Macroscopic Quantum Phenomena: Tests of Quantum Mechanics 

The correctness of quantum mechanics has been verified in numerous situations. A particularly strong test of quantum mechanics was suggested by Bell, who showed that the predictions of all classical theories, based as they are on the assumptions of local realism, contradict those of quantum mechanics. Later work by Greenberger, Horne, and Zeilinger showed that the GHZ phenomena also contradicts all classical theories. Experimental tests of Bells inequality performed to date support quantum mechanics (No experimental test of the GHZ phenomenon has yet been attempted). However, such tests have been so far restricted to microscopic systems in the sense that one particle is at a detector at a time.  
Our interest here in the first part of this thesis is in tests of quantum mechanics against local realistic theories in macroscopic or mesoscopic systems where there is a significant number of particles incident on each analyser. The states considered in the first two chapters are not simple quantum superpositions of macroscopically distinct states, but we nevertheless show how one can obtain tests of quantum mechanics in situations involving large numbers of particles. A more elementary macroscopic quantum state, and one in which the deviation from classical interpretations is striking, is the Schrodinger Cat state considered by Schrodinger in his famous "Schrodinger Cat" paradox. In Chapter Three we consider a scheme for generating such a state. 

The Quantum Brownian Motion Master Equation 

The second section of this thesis involves an examination of various aspects of the Quantum Brownian Motion Master Equation. We begin with a discussion of the recent problem occurring from the study of the quantum Brownian motion (QBM) master equation, which can occur because the QBM master equation is not of the Lindblad form. We examine two specific examples, namely the damped free particle and the two level atom. More specifically, in the case of the evolution of a free particle, we show that the equation of motion for the Wigner function (which is exactly the same as the Fokker-Planck equation for classical Brownian motion) gives unphysical results if the initial position distribution is well localised. In the case of the two level atom we show that unphysical results can also occur even in the steady state. 
The last chapter of the thesis involves using the quantum Brownian motion master equation to estimate the rate of diagonalisation of the off diagonal elements of a Fermion system. These elements contain the "quantum information" and hence knowledge of how long they exist can determine the type of model required to describe the semiconductor medium. Using a very simplistic approach we can show that there are two main time scales present and for normal parameters one of these is very small. If we neglect electron-electron scattering we can show that the the many electron system solution is simply a product of the one electron solutions.

year: 1994

title: Full field image ranger hardware

authors: Payne, Andrew D.

subjects: imaging

abstract: We describe the hardware designed to implement a full field heterodyning imaging system. Comprising three key components - a light source, high speed shutter and a signal generator - the system is expected to be capable of simultaneous range measurements to millimetre precision over the entire field of view. Current modulated laser diodes provide the required illumination, with a bandwidth of 100 MHz and peak output power exceeding 600 mW. The high speed shutter action is performed by gating the cathode of an image intensifier, driven by a 50 Vpp waveform with 3.5 ns rise and fall times. A direct digital synthesiser, with multiple synchronised channels, provides high stability between its outputs, 160 MHz bandwidth and tuning of 0.1 Hz.

text: Full field image ranger hardware We describe the hardware designed to implement a full field heterodyning imaging system. Comprising three key components - a light source, high speed shutter and a signal generator - the system is expected to be capable of simultaneous range measurements to millimetre precision over the entire field of view. Current modulated laser diodes provide the required illumination, with a bandwidth of 100 MHz and peak output power exceeding 600 mW. The high speed shutter action is performed by gating the cathode of an image intensifier, driven by a 50 Vpp waveform with 3.5 ns rise and fall times. A direct digital synthesiser, with multiple synchronised channels, provides high stability between its outputs, 160 MHz bandwidth and tuning of 0.1 Hz.

year: 2006

title: Community-university collaborations: creating hybrid research and collective identities

authors: Cave, Jennifer Barbara Jane

subjects: collaborative

abstract: In this article we explore the politics of community-university collaborative research and activism. We are scholars based in universities as well as members of various 'communities'-queer, Pasifika and Māori-hence we regularly venture beyond the formal research spaces of the academy and enter into critical collaborative research with others working in 'the community'. In what follows we first outline collaborative community-based research literature that advocates hybrid research collectivities. Second, we give some context and background to our methodologies that have enabled us to re-think collaborative research. Third, examples from our research are offered to illustrate the ways in which collaborative research constructs new collective identities. Finally, we conclude by arguing that social science scholars working across university-community boundaries may expand and multiply hybrid research collectives, and thereby effect positive social change at many levels

text: Community-university collaborations: creating hybrid research and collective identities In this article we explore the politics of community-university collaborative research and activism. We are scholars based in universities as well as members of various 'communities'-queer, Pasifika and Māori-hence we regularly venture beyond the formal research spaces of the academy and enter into critical collaborative research with others working in 'the community'. In what follows we first outline collaborative community-based research literature that advocates hybrid research collectivities. Second, we give some context and background to our methodologies that have enabled us to re-think collaborative research. Third, examples from our research are offered to illustrate the ways in which collaborative research constructs new collective identities. Finally, we conclude by arguing that social science scholars working across university-community boundaries may expand and multiply hybrid research collectives, and thereby effect positive social change at many levels

year: 2012