We report the experimental realization of squeezed quantum states of light, tailored for new applications in quantum communication and metrology. Squeezed states in a broad Fourier frequency band down to 1 Hz have been observed for the first time. Nonclassical properties of light in such a low frequency band are required for high efficiency quantum information storage in electromagnetically induced transparency (EIT) media. The states observed also cover the frequency band of ultra-high precision laser interferometers for gravitational wave detection and can be used to reach the regime of quantum non-demolition interferometry. Furthermore, they cover the frequencies of motion of heavy macroscopic objects and might therefore support attempts to observe entanglement in our macroscopic world.
We report the experimental realization of squeezed quantum states of light, tailored for new applications in quantum communication and metrology. Squeezed states in a broad Fourier frequency band down to 1 Hz have been observed for the first time. Nonclassical properties of light in such a low frequency band are required for high efficiency quantum information storage in electromagnetically induced transparency (EIT) media. The states observed also cover the frequency band of ultra-high precision laser interferometers for gravitational wave detection and can be used to reach the regime of quantum non-demolition interferometry. Furthermore, they cover the frequencies of motion of heavy macroscopic objects and might therefore support attempts to observe entanglement in our macroscopic world.
We report the experimental realization of squeezed quantum states of light, tailored for new applications in quantum communication and metrology. Squeezed states in a broad Fourier frequency band down to 1 Hz have been observed for the first time. Nonclassical properties of light in such a low frequency band are required for high efficiency quantum information storage in electromagnetically induced transparency ( EIT) media. The states observed also cover the frequency band of ultra-high precision laser interferometers for gravitational wave detection and can be used to reach the regime of quantum non-demolition interferometry. Furthermore, they cover the frequencies of motion of heavy macroscopic objects and might therefore support attempts to observe entanglement in our macroscopic world.
Squeezed states of light were observed for the first time in 1985.Since then they have developed into an important nonclassical tool in the field of high-precision metrology, for instance in gravitational wave detection, as well as in the field of quantum information, e.g. for teleportation and quantum cryptography.For all these applications a strong squeezing factor is beneficial.This thesis presents a new benchmark value for squeezed light from non-monolithic squeezed-light sources.By means of parametric down-conversion, squeezed states at a wavelength of 1064 nm were generated and a nonclassical noise suppression of 12.3 dB was observed.In contrast to a monolithic resonator, the resonance frequency of this squeezed-light source can be adjusted to a downstream experiment.In an additional experiment this squeezed-light source was utilized to determine the quantum efficiency of photo diodes.The applied method permits high precision since strong squeezing is sensitive to even low values of optical loss.In view of the application of squeezed light in future-generation gravitational wave detectors and quantum information science, a dedicated squeezed-light source was developed and at a wavelength of 1550 nm squeezing in the continuous-wave regime was observed for the first time.These squeezed states were employed to quantumenhance the sensitivity of a fiber-based Sagnac interferometer.Thus the compatibility of squeezing at 1550 nm with fiber-based quantum communication was demonstrated.Furthermore, upon thorough optimization of the squeezed-light generation and detection at 1550 nm, a quantum noise suppression of 12.3 dB was measured.Moreover, squeezing in the Fourier audio-band was observed for the first time.The findings presented in this thesis constitute key research towards the squeezed-light technology at 1550 nm as it is required for future gravitational wave detectors such as the recently proposed Einstein Telescope.
The detection of gravitational waves has ushered in a new era of observing the universe. Quantum resource advantages offer significant enhancements to the sensitivity of gravitational wave observatories. While squeezed states for ground-based gravitational wave detection have received marked attention, the generation of squeezed states suitable for mid-to-low-frequency detection has remained unexplored. To address the gap in squeezed state optical fields at ultra-low frequencies, we report on the first direct observation of a squeezed vacuum field until Fourier frequency of 4 millihertz with the quantum noise reduction of up to 8.0 dB, by the employment of a multiple noise suppression scheme. Our work provides quantum resources for future gravitational wave observatories, facilitating the development of quantum precision measurement.
Squeezed-state enhanced audio-frequency signal measurement is crucial for some special applications, such as gravitational wave detection. But generation of squeezed state of light at such frequency is more difficult than that at megahertz-frequency. In this paper we propose an experimental scheme to measure low-frequency phase signal with high-frequency squeezing. To utilize the high-frequency sidebands of the squeezed light, a two-frequency intense laser is applied in the interferometry instead of a single-frequency laser as usual. This technique is in the reach of modern quantum optics technology.
Squeezing of light's quantum noise requires temporal rearranging of photons. This again corresponds to creation of quantum correlations between individual photons. Squeezed light is a nonclassical manifestation of light with great potential in high-precision quantum measurements, for example, in the detection of gravitational waves [C. M. Caves, Phys. Rev. D 23, 1693 (1981)10.1103/PhysRevD.23.1693]. Equally promising applications have been proposed in quantum communication [H. P. Yuen and J. H. Shapiro, IEEE Trans. Inf. Theory 24, 657 (1978)10.1109/TIT.1978.1055958]. However, after 20 years of intensive research doubts arose whether strong squeezing can ever be realized as required for eminent applications. Here we show experimentally that strong squeezing of light's quantum noise is possible. We reached a benchmark squeezing factor of 10 in power (10 dB). Thorough analysis reveals that even higher squeezing factors will be feasible in our setup.
Squeezed light, a prominent non-classical state of light, exhibits reduced quantum noise in one quadrature component below the standard quantum limit (SQL). The property enables quantum-enhanced precision measurements, surpassing the SQL in quantum sensing applications. This review comprehensively introduces the fundamental concepts, classifications, and experimental generation techniques of squeezed light. It further explores its pivotal role and recent advances in diverse quantum sensing domains, including interferometry, gravitational wave detection, magnetometry, force sensing, biomedical sensing, and quantum radar. The review covers theoretical foundations of squeezed states (including quadrature operators and classification schemes, experimental generation techniques in atomic ensembles, nonlinear crystals, and fibers), fundamentals of quantum sensing with squeezed light (from quantum noise theory to quantum-enhanced metrology), and quantum-enhanced sensing applications across the aforementioned domains. Finally, future challenges and opportunities in the field are discussed.