Details
Original language  English 

Qualification  Doctor rerum naturalium 
Awarding Institution  
Supervised by 

Date of Award  21 Feb 2023 
Place of Publication  Hannover 
Publication status  Published  2023 
Abstract
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Hannover, 2023. 153 p.
Research output: Thesis › Doctoral thesis
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TY  BOOK
T1  Quantum metrology using tailored nonclassical states
AU  Junker, Jonas
N1  Doctoral thesis
PY  2023
Y1  2023
N2  Squeezed states of light play a significant role in various technologies ranging from highprecision metrology such as gravitational wave detection to quantum information.These quantum states are prepared to carry particular characteristics depending on their application. For instance, some applications require squeezing in one, others only in the combination of two distinct optical modes. Furthermore, squeezing can appear constant for all frequencies or frequencydependently. In this thesis, novel quantum optical methods employing different, tailored nonclassical light sources, are developed and described. The individual squeezed states are controlled and characterised, each tailored for a particular application. In highprecision spectroscopy, the measurement sensitivity is often limited by technical noise at low frequencies. The first publication shows that small phase signals at lowfrequency are resolvable without increasing the laser power. We use a phasemodulated field, shifting the signal to high frequencies where technical noise is circumvented. In addition, the field is squeezed by 6 dB at high frequencies to reduce shot noise arising from quantum fluctuations. Our approach resolves subshotnoise signals at 100 Hz and 20 kHz on a reduced noise floor. In optomechanical sensors such as gravitational wave detectors, the fundamental measurement limitation arises from the combination of shot noise and quantum backaction noise induced by quantum radiation pressure noise. A conventional fixedquadrature squeezed state generated by a resonant optical parametric oscillator (OPO) can only fight one of these two contributions simultaneously. To cancel both quantum noise contributions, a particularly frequencydependent squeezed state is required. Our second publication shows that a detuned OPO generates frequencydependent squeezing. It can be used as an approximate effectivenegative mass oscillator in an alloptical coherent quantum noise cancellation scheme and is suitable to coherently cancel quantum noise. Our generated state, which is reconstructed by quantum tomography, rotating over megahertz frequencies, exhibits a rotation angle of 39° and a maximal squeezing degree of 5.5 dB. Twomode squeezed quantum states are resources required in modern applications such as quantum information processing. In the third publication, we address the challenge of determining the ten independent entries of a twomode squeezed state’s covariance matrix to fully characterise the quantum state. We demonstrate a full reconstruction of a 7 dB twomode squeezed state using only a single polarisationsensitive homodyne detector, which avoids additional optics and potential loss channels. The findings of this thesis are relevant for experiments in highprecision quantum metrology, e.g. in spectroscopy or gravitational wave detectors operating at the standard quantum limit. The insights gained on the generating and handling nonclassical states enable advances in quantum information technology.
AB  Squeezed states of light play a significant role in various technologies ranging from highprecision metrology such as gravitational wave detection to quantum information.These quantum states are prepared to carry particular characteristics depending on their application. For instance, some applications require squeezing in one, others only in the combination of two distinct optical modes. Furthermore, squeezing can appear constant for all frequencies or frequencydependently. In this thesis, novel quantum optical methods employing different, tailored nonclassical light sources, are developed and described. The individual squeezed states are controlled and characterised, each tailored for a particular application. In highprecision spectroscopy, the measurement sensitivity is often limited by technical noise at low frequencies. The first publication shows that small phase signals at lowfrequency are resolvable without increasing the laser power. We use a phasemodulated field, shifting the signal to high frequencies where technical noise is circumvented. In addition, the field is squeezed by 6 dB at high frequencies to reduce shot noise arising from quantum fluctuations. Our approach resolves subshotnoise signals at 100 Hz and 20 kHz on a reduced noise floor. In optomechanical sensors such as gravitational wave detectors, the fundamental measurement limitation arises from the combination of shot noise and quantum backaction noise induced by quantum radiation pressure noise. A conventional fixedquadrature squeezed state generated by a resonant optical parametric oscillator (OPO) can only fight one of these two contributions simultaneously. To cancel both quantum noise contributions, a particularly frequencydependent squeezed state is required. Our second publication shows that a detuned OPO generates frequencydependent squeezing. It can be used as an approximate effectivenegative mass oscillator in an alloptical coherent quantum noise cancellation scheme and is suitable to coherently cancel quantum noise. Our generated state, which is reconstructed by quantum tomography, rotating over megahertz frequencies, exhibits a rotation angle of 39° and a maximal squeezing degree of 5.5 dB. Twomode squeezed quantum states are resources required in modern applications such as quantum information processing. In the third publication, we address the challenge of determining the ten independent entries of a twomode squeezed state’s covariance matrix to fully characterise the quantum state. We demonstrate a full reconstruction of a 7 dB twomode squeezed state using only a single polarisationsensitive homodyne detector, which avoids additional optics and potential loss channels. The findings of this thesis are relevant for experiments in highprecision quantum metrology, e.g. in spectroscopy or gravitational wave detectors operating at the standard quantum limit. The insights gained on the generating and handling nonclassical states enable advances in quantum information technology.
U2  10.15488/13411
DO  10.15488/13411
M3  Doctoral thesis
CY  Hannover
ER 