title: Squeezed states and quantum nondemolition measurements

authors: Milburn, Gerard James

abstract: The first four chapters of this thesis are concerned with the detailed mathematical and physical properties of special minimum uncertainty states of the electromagnetic field: the “squeezed states”. These are states with reduced quantum fluctuations in certain observables (the quadrature phase amplitudes).

In chapter two it is shown that the one mode and two mode squeezed states are obtained by acting on the vacuum state with elements of the sympletic group in one and two dimensions respectively. 

In chapter three properties of squeezed states in a quantum optical context are investigated. The complex P representation of Drummond and Gardiner is shown to be especially useful for discussing the non-classical statistics of these states, and the complex P-representation for a squeezed state is obtained. An analysis of the effect of irreversible dynamics on squeezed states is also given. 

In chapter four a detailed analysis of three devices proposed to produce squeezed states; degenerate parametric oscillation, two photon absorption and dispersive optical bistability, is presented. It is shown in an exact, fully quantum treatment that the reduction of fluctuations obtainable in all these devices is limited, when operated in a steady state regime. The greatest reduction of fluctuations (a factor of two) occurs in the parametric oscillator operated at threshold. The addition of a second driving field in this device enables the direction of squeezing to be changed.

The final two chapters are given over to a discussion of Quantum Non Demolition (QND) measurements. In chapter five a particular QND scheme (back action evading) is analysed. This is based on a parametric amplification interaction. The complex p representation is used to discuss the non-unitary effects of damping and state reduction in a unified way. It is shown that the parametric amplifier, despite being non back action evading, is useful for making QND measurements. 

Finally in chapter six, two quantum counting QND schemes, based on quantum optical four wave mixing interactions, are analysed. The effect of state reduction is included, thus enabling an analysis of a measurement sequence.

text: Squeezed states and quantum nondemolition measurements The first four chapters of this thesis are concerned with the detailed mathematical and physical properties of special minimum uncertainty states of the electromagnetic field: the “squeezed states”. These are states with reduced quantum fluctuations in certain observables (the quadrature phase amplitudes).

In chapter two it is shown that the one mode and two mode squeezed states are obtained by acting on the vacuum state with elements of the sympletic group in one and two dimensions respectively. 

In chapter three properties of squeezed states in a quantum optical context are investigated. The complex P representation of Drummond and Gardiner is shown to be especially useful for discussing the non-classical statistics of these states, and the complex P-representation for a squeezed state is obtained. An analysis of the effect of irreversible dynamics on squeezed states is also given. 

In chapter four a detailed analysis of three devices proposed to produce squeezed states; degenerate parametric oscillation, two photon absorption and dispersive optical bistability, is presented. It is shown in an exact, fully quantum treatment that the reduction of fluctuations obtainable in all these devices is limited, when operated in a steady state regime. The greatest reduction of fluctuations (a factor of two) occurs in the parametric oscillator operated at threshold. The addition of a second driving field in this device enables the direction of squeezing to be changed.

The final two chapters are given over to a discussion of Quantum Non Demolition (QND) measurements. In chapter five a particular QND scheme (back action evading) is analysed. This is based on a parametric amplification interaction. The complex p representation is used to discuss the non-unitary effects of damping and state reduction in a unified way. It is shown that the parametric amplifier, despite being non back action evading, is useful for making QND measurements. 

Finally in chapter six, two quantum counting QND schemes, based on quantum optical four wave mixing interactions, are analysed. The effect of state reduction is included, thus enabling an analysis of a measurement sequence.

year: 1982

title: Retroviruses in the common brush-tailed possum (Trichosurus vulpecula)

authors: Baillie, Gregory John

abstract: This study details the search for, and characterisation of, retroviruses in a marsupial, the common brush-tailed possum (Trichosurus vulpecula). Initial efforts were directed at detecting exogenous retroviruses in possums, but the majority of the work described in this thesis involved the isolation and characterisation of a possum endogenous retrovirus.

Endogenous retroviruses were detected in possum genomic DNA by PCR amplification using degenerate primers derived from the retroviral pol gene. Cloning, sequencing, and analysis of these PCR products revealed the presence of several families of endogenous retroviruses in the possum genome.

Reverse transcriptase activity was detected in the blood of all possums tested using the product enhanced reverse transcriptase (PERT) assay. RT-PCR was performed on RNA isolated from possum blood plasma using the pol-derived degenerate primers. Cloning and sequencing of the products indicated that a homogeneous retroviral RNA species was present in the blood of possums, and that this RNA was related to, but not identical to, the endogenous possum retroviruses already detected.

A 3'-RACE approach was used to amplify the majority of the 3' end of the possum retroviral RNA. The subsequent discovery that this RNA species was derived from an endogenous retrovirus in the possum genome allowed amplification of the remainder of the genome by a combination of PCR, single primer PCR, and RT-PCR. The sequences were assembled into a contiguous sequence, the TvERV-K1 contig. In addition, a near-full-length TvERV-K1-related fragment, was amplified from possum genomic DNA, cloned, and sequenced. It was named pTvERV-K2. The TvERV-K elements are the first full-length marsupial retrovirus sequences to be reported.

Analysis of the sequences of the TvERV-K1 contig and pTvERV-K2 revealed most of the regulatory regions required for replication of a retroviral genome, as well as uninterrupted, or minimally interrupted, open reading frames (ORFs) for the gag, pro, and pol genes. Only a short region of sequence with homology to the Env proteins of other retroviruses was detected. All of the TvERV-K proteins displayed highest homology to those of the simian type D retroviruses. Likewise, phylogenetic analysis using the deduced amino acid sequences of the Pro and Pol proteins, placed the possum endogenous retrovirus with the exogenous and endogenous type D retroviruses of Old World and New World monkeys. Thus, a cross-species transmission event - from marsupials to primates, from primates to marsupials, or from an unidentified source to both marsupials and primates - appears to have occurred.

There are 15-20 copies of the TvERV-K element in the possum genome, as determined by Southern hybridisation. However, integration sites appeared to be variable between possums, suggesting recent (or ongoing) retrotranspositional activity. Both PCR and Southern hybridisation analyses suggest that TvERV-K elements shorter than those from which the TvERV-K1 contig and pTvERV-K2 were derived are present in the possum genome. 

The implications of these findings are discussed.

text: Retroviruses in the common brush-tailed possum (Trichosurus vulpecula) This study details the search for, and characterisation of, retroviruses in a marsupial, the common brush-tailed possum (Trichosurus vulpecula). Initial efforts were directed at detecting exogenous retroviruses in possums, but the majority of the work described in this thesis involved the isolation and characterisation of a possum endogenous retrovirus.

Endogenous retroviruses were detected in possum genomic DNA by PCR amplification using degenerate primers derived from the retroviral pol gene. Cloning, sequencing, and analysis of these PCR products revealed the presence of several families of endogenous retroviruses in the possum genome.

Reverse transcriptase activity was detected in the blood of all possums tested using the product enhanced reverse transcriptase (PERT) assay. RT-PCR was performed on RNA isolated from possum blood plasma using the pol-derived degenerate primers. Cloning and sequencing of the products indicated that a homogeneous retroviral RNA species was present in the blood of possums, and that this RNA was related to, but not identical to, the endogenous possum retroviruses already detected.

A 3'-RACE approach was used to amplify the majority of the 3' end of the possum retroviral RNA. The subsequent discovery that this RNA species was derived from an endogenous retrovirus in the possum genome allowed amplification of the remainder of the genome by a combination of PCR, single primer PCR, and RT-PCR. The sequences were assembled into a contiguous sequence, the TvERV-K1 contig. In addition, a near-full-length TvERV-K1-related fragment, was amplified from possum genomic DNA, cloned, and sequenced. It was named pTvERV-K2. The TvERV-K elements are the first full-length marsupial retrovirus sequences to be reported.

Analysis of the sequences of the TvERV-K1 contig and pTvERV-K2 revealed most of the regulatory regions required for replication of a retroviral genome, as well as uninterrupted, or minimally interrupted, open reading frames (ORFs) for the gag, pro, and pol genes. Only a short region of sequence with homology to the Env proteins of other retroviruses was detected. All of the TvERV-K proteins displayed highest homology to those of the simian type D retroviruses. Likewise, phylogenetic analysis using the deduced amino acid sequences of the Pro and Pol proteins, placed the possum endogenous retrovirus with the exogenous and endogenous type D retroviruses of Old World and New World monkeys. Thus, a cross-species transmission event - from marsupials to primates, from primates to marsupials, or from an unidentified source to both marsupials and primates - appears to have occurred.

There are 15-20 copies of the TvERV-K element in the possum genome, as determined by Southern hybridisation. However, integration sites appeared to be variable between possums, suggesting recent (or ongoing) retrotranspositional activity. Both PCR and Southern hybridisation analyses suggest that TvERV-K elements shorter than those from which the TvERV-K1 contig and pTvERV-K2 were derived are present in the possum genome. 

The implications of these findings are discussed.

year: 1999

title: A late-Holocene and prehistoric record of environmental change from Lake Waikaremoana, New Zealand

authors: Newnham, Rewi M.

subjects: Palynology

abstract: Further evidence in support of a late pre-European (Polynesian) settlement of New Zealand is provided by an 1850-year-long tephropalynological record from a remote region in New Zealand's North Island. The earliest unequivocally anthropogenic forest clearance is estimated from sedimentation rates to have occurred c. 375 14C years BP (c. ad 1523–1631), although the radiocarbon chronology, shown by tephrochron ology to be erroneous due to hard-water effects, suggested this occurred c. 900 years earlier. Delineation of the anthropogenic era, and the distinction between human activity and other agents of environmental change in the pollen/spore diagram, are supported by cluster analysis and detrended correspondence analysis. Two distinct phases of forest clearance are evident during the pre-European era, reflecting local changes either in population pressure or settlement patterns. We note that the lull between the two phases of forest clearance coincides with the maximum of the ‘Little Ice Age’ within the period c. late ad 1600s to early 1800s.

text: A late-Holocene and prehistoric record of environmental change from Lake Waikaremoana, New Zealand Further evidence in support of a late pre-European (Polynesian) settlement of New Zealand is provided by an 1850-year-long tephropalynological record from a remote region in New Zealand's North Island. The earliest unequivocally anthropogenic forest clearance is estimated from sedimentation rates to have occurred c. 375 14C years BP (c. ad 1523–1631), although the radiocarbon chronology, shown by tephrochron ology to be erroneous due to hard-water effects, suggested this occurred c. 900 years earlier. Delineation of the anthropogenic era, and the distinction between human activity and other agents of environmental change in the pollen/spore diagram, are supported by cluster analysis and detrended correspondence analysis. Two distinct phases of forest clearance are evident during the pre-European era, reflecting local changes either in population pressure or settlement patterns. We note that the lull between the two phases of forest clearance coincides with the maximum of the ‘Little Ice Age’ within the period c. late ad 1600s to early 1800s.

year: 1998