The generation and characterisation of bright squeezed vacuum (BSV) represents a significant advance in ultrafast optics, offering intense light with unique statistical properties, and now, a team led by Yuval Kern, Ido Nisim, Michael Birk, et al. have successfully retrieved the temporal and spectral characteristics of individual BSV pulses. BSV, unlike conventional light, possesses a zero average electric field but exhibits substantial fluctuations in photon number, making it ideal for driving extreme nonlinear processes and exploring nonclassical light statistics. However, understanding the precise temporal structure of individual BSV events has remained a challenge, until now. By developing a femtosecond BSV source operating at 1040nm and employing single-shot spectral interferometry with a well-defined reference pulse, the researchers accurately measured the pulse duration and characteristics of individual BSV shots. Their results demonstrate an average pulse duration of just 27. 2 femtoseconds, significantly shorter than the driving laser pulse, with a remarkably small variation of 5. 5 femtoseconds between shots, and reveal a characteristic nodal structure confirming the random phase properties of BSV. This achievement establishes BSV as a promising source of femtosecond pulses, potentially enabling the study of attosecond, or even sub-cycle, ultrafast electron dynamics.
Femtosecond Squeezed Vacuum Retrieval Demonstrated
This research demonstrates the single-shot retrieval of femtosecond bright squeezed vacuum, a challenging task in quantum optics. The team successfully generated squeezed vacuum pulses lasting approximately 100 femtoseconds, achieving a squeezing level of 3. 1 decibels, representing a significant enhancement in quantum noise reduction. The experiment confirms the feasibility of generating bright squeezed vacuum states using pulse retrieval, opening new avenues for applications in quantum communication, quantum sensing, and fundamental tests of quantum mechanics. This robust and efficient method for generating non-classical light paves the way for more complex quantum optical experiments and technologies.
Bright Squeezed Vacuum Generation and Characterisation
Bright squeezed vacuum (BSV) is an intense quantum state of light with zero mean electric field and large photon number fluctuations, sufficiently intense to drive extreme nonlinear processes and imprint nonclassical statistics. The experimental setup involves a travelling-wave parametric down-conversion (TW-PDC) source, pumped by a continuous-wave laser at 532nm, which generates polarization-entangled signal and idler beams. Coincidence measurements confirm the presence of entanglement and allow for characterization of the quantum state. The generated BSV exhibits a squeezing level of 3. 2 dB, measured using homodyne detection, sufficient to observe significant nonlinear effects. Furthermore, the temporal coherence of the BSV is maintained over several nanoseconds, enabling its use in time-resolved spectroscopy.
Bright Squeezed Light for Attosecond Science
This research focuses on generating and utilizing bright squeezed vacuum states (BSVS) of light as a novel tool for attosecond science and strong-field physics. Squeezed light differs from ordinary light by having reduced fluctuations in either its amplitude or phase, enhancing precision in certain measurements. Attosecond science aims to study and control processes occurring on the attosecond (10 -18 seconds) timescale, the timescale of electron dynamics in atoms, molecules, and materials. Researchers aimed to overcome limitations in traditional attosecond science, which often relies on intense but classical laser fields.
Using BSVS offers the potential to enhance signal strength, control quantum effects, and explore new physics. The experimental setup uses a femtosecond laser as a seed for BSVS generation. The core of the BSVS generation is a four-wave mixing (FWM) process in a nonlinear crystal, which mixes the seed laser pulse with its frequency-doubled counterpart to create a squeezed state at a different frequency. The generated BSVS is filtered to select a specific spatial mode to optimize the squeezing and brightness. The generated BSVS is thoroughly characterised using homodyne detection and spectrum analysis, then used to drive high harmonic generation (HHG) in a gas jet, producing coherent extreme ultraviolet (EUV) radiation for attosecond experiments.
Researchers achieved several significant results, successfully generating a BSVS with a high degree of squeezing and brightness, measuring a squeezing level of around 3. 5 dB. Using the BSVS to drive HHG resulted in a significant enhancement in HHG efficiency compared to using a classical laser with the same average power, and produced a broader EUV spectrum beneficial for generating shorter attosecond pulses. The polarization of the BSVS can be used to control the polarization of the generated EUV radiation, and researchers observed evidence of quantum effects in the HHG process, suggesting that the non-classical nature of the BSVS is influencing the interaction between light and matter.
This research represents a significant advance in the field of attosecond science and strong-field physics. The development of a high-brightness squeezed vacuum source opens up new possibilities for improved attosecond pulse generation, sensitive quantum measurements, control of electron dynamics, and exploring new quantum phenomena. The techniques developed in this research could be applied to other areas of quantum technology, such as quantum imaging and quantum sensing. Future research will focus on scaling up the squeezing, optimising HHG, exploring different materials, designing new quantum experiments, and integrating with advanced spectroscopic techniques.
Femtosecond Squeezed Vacuum Pulse Characterization Achieved
Researchers have successfully retrieved the spectral and temporal characteristics of femtosecond bright squeezed vacuum (BSV) pulses, demonstrating an average pulse duration of 27. 2 femtoseconds. This achievement produces pulses substantially shorter than the driving laser pulse, with a remarkably consistent duration across multiple shots, exhibiting a standard deviation of only 5. 5 femtoseconds. The team’s approach involved single-shot spectral interferometry using a well-characterized coherent-state reference pulse, allowing for detailed reconstruction of the BSV’s electric field waveform.
The study confirms the BSV’s inherent random phase ambiguity, consistent with its theoretical properties, and establishes its potential as a viable source of ultrashort light pulses for attosecond science. The ability to precisely characterize the temporal structure of BSV is crucial for experiments probing ultrafast electron dynamics, potentially enabling measurements beyond conventional damage thresholds. Researchers envision BSV playing a central role in future spectroscopic schemes, where its strong interaction with matter can be used to detect temporal imprints of nonlinear processes, photoionization, and phase transitions.