Squeezed light is a key resource in quantum metrology and quantum information science. It is primarily generated through nonlinear optical interactions, where the degree of squeezing is set by the nonlinearity of the medium. Here, we modulate the third-order nonlinear response of a dielectric with strong ultrafast laser fields to control squeezed light generation on attosecond time scales. By tuning a sub-cycle phase delay between the input femtosecond pulses, we switch the generated light between amplitude-squeezed and phase-squeezed states. We measure the quantum noise using a frequency-resolved balanced homodyne detection scheme that extracts field quadratures in many frequency modes simultaneously. From these measurements we obtain the complete coherency matrix containing quadrature correlations across the frequency modes of the pulse. These results enable quantum light sources with sub-cycle control of squeezing and open a route to transduction of dynamical quantum correlations in matter to quantum correlations in electric fields.
Comments
v2: New author ME added, substantially revised, calibrated squeezing value added, fourth-cumulant analysis added
Squeezed light is a key resource in quantum metrology and quantum information science. It is primarily generated through nonlinear optical interactions, where the degree of squeezing is set by the nonlinearity of the medium. Here, we modulate the third-order nonlinear response of a dielectric with strong ultrafast laser fields to control squeezed light generation on attosecond time scales. By tuning a sub-cycle phase delay between the input femtosecond pulses, we switch the generated light between amplitude-squeezed and phase-squeezed states. We measure the quantum noise using a frequency-resolved balanced homodyne detection scheme that extracts field quadratures in many frequency modes simultaneously. From these measurements we obtain the complete coherency matrix containing quadrature correlations across the frequency modes of the pulse. These results enable quantum light sources with sub-cycle control of squeezing and open a route to transduction of dynamical quantum correlations in matter to quantum correlations in electric fields.
Nonclassical states of light are central resources for quantum metrology and quantum information, yet most high performance squeezing platforms operate in narrowband or continuous-wave regimes where the quantum noise is effectively stationary. This work advances ultrafast quantum optics by demonstrating how squeezed states can be generated, measured, and engineered on femtosecond and attosecond time scales, so that quantum fluctuations become a controllable property of the optical waveform itself. In this work, broadband few-cycle coherent drivers are produced using the light field synthesizer (LFS) setup that coherently combines UV/VIS/NIR channels with independently adjustable delays and amplitudes. Ultrafast squeezed light is generated via degenerate four-wave mixing (DFWM) in fused silica using a three-beam interaction geometry, implemented as a quantum light field squeezer (QLFS) that enables quasi-collinear phase matching across a wide bandwidth. A metrology framework compatible with ultrashort pulses is developed: amplitude (intensity) uncertainty is extracted from shot-to-shot spectral statistics, while relative phase fluctuations are retrieved from spectral-interference fringes in channel-overlap regions. These observables are connected to a displaced squeezed state model by fitting variance expressions, enabling phase-space visualization through Wigner function reconstruction. Beyond static squeezing, the QLFS provides attosecond-resolved control of the generated quantum state by tuning inter-pulse delay and phase matching geometry, allowing the redistribution of uncertainty between conjugate quadratures and revealing time-dependent (sub-cycle) structure of the intensity uncertainty within the optical cycle. Finally, the work extends ultrafast quantum optics into solid-state systems by demonstrating squeezed light driven tunneling in a graphene-silicon-graphene phototransistor, where state-dependent modulation of current noise is observed alongside simultaneous optical uncertainty measurements. Together, these results establish a practical route to waveform-level quantum state engineering and motivate future ultrafast quantum metrology, strong field quantum optics control, and hybrid photonic electronic quantum technologies.
The generation and control of extreme ultraviolet (XUV) radiation by high harmonic generation (HHG) have advanced ultrafast science, providing direct insights into electron dynamics on their natural time scale. Attosecond science has established the capability to resolve ultrafast quantum phenomena in matter by characterizing and controlling the classical properties of the high harmonics. Recent theoretical proposals have introduced novel schemes for generating and manipulating XUV HHG with distinct quantum features, paving the way to attosecond quantum optics. In this work, we transfer fundamental concepts in quantum optics into attosecond science. By driving the HHG process with a combination of an infrared bright squeezed vacuum (BSV, a non-classical state of light), and a strong coherent field, we imprint the quantum correlations of the input BSV onto both the ultrafast electron wavefunction and the harmonics' field. Performing in-situ HHG interferometry provides an insight into the underlying sub-cycle dynamics, revealing squeezing in the statistical properties of one of the most fundamental strong-field phenomena -- field induced tunneling. Our measurement allows the reconstruction of the quantum state of the harmonics through homodyne-like tomography, resolving correlated fluctuations in the harmonic field that mirror those of the input BSV. By controlling the delay between the two driving fields, we manipulate the photon statistics of the emitted attosecond pulses with sub-cycle accuracy. The ability to measure and control quantum correlations in both electrons and XUV attosecond pulses establishes a foundation for attosecond electrodynamics, manipulating the quantum state of electrons and photons with sub-cycle precision.
Modern quantum optics primarily operates in the quasistationary regime, isolated from the intrinsic timescales of ultrafast optical fields. Pushing these boundaries into the femtosecond and attosecond domains is a critical frontier. Here, we generate, shape, and interrogate the quantum state of an ultrafast squeezed light field. Our optical metrology reveals a highly dynamic, time dependent squeezing distribution across individual half cycles of the electric field. Incorporating this intracycle squeezing into strong field simulations demonstrates that the temporal redistribution of quantum uncertainty fundamentally reshapes the quantum strong field physics of high harmonic emission. Furthermore, we achieve attosecond scale control of the squeezed state, visualized through inferred effective Wigner representations. Finally, we show that ultrafast squeezed light encodes its quantum properties into a photoinduced tunneling current within a petahertz phototransistor with subfemtosecond resolution, demonstrating a direct optical electronic quantum coupling. This work lays the foundation for the emerging field of ultrafast quantum optics and unlocks new avenues for high speed quantum communication and photonics.
In quantum optics, quantization of the electromagnetic field typically occurs in a finite volume - a cavity - which results in discrete frequency modes where photons are created, annihilated and exchanged between such modes. As a result, evolution of quantum optical states is periodic in the carrier wave of the field, measurement protocols return cycle-averaged information, and any sub-cycle evolution that is foundational to many light-matter interactions, especially at high field strengths, remains hidden. Adapting an attosecond technique, here we capture the electric-field evolution of a quantum optical state, femtosecond bright squeezed vacuum, with sub-cycle precision. We find that it consists of many stochastic, time-localized bursts within each pump pulse whose phase randomly switches between two values. We exploit the random phase flips to generate quantum random bit sequences with a generation rate that can reach petahertz frequencies. In addition, the sub-cycle resolution allows us to measure coherence functions of the waveforms between any two times, which we explain with a superposition of time-limited modes. These results bridge attosecond metrology and quantum optics and pave the way to measuring quantum light-matter interactions as they evolve on a few-femtosecond time scale, and integrate quantum randomness in petahertz electronics.
Advancements in quantum optics and squeezed light generation have revolutionized various fields of quantum science over the past three decades, with notable applications such as gravitational wave detection. Here, we extend the use of squeezed light to the realm of ultrafast quantum science. We demonstrate the generation of the shortest ultrafast synthesized quantum light pulses spanning 0.33 to 0.73 PHz by a degenerate four-wave mixing nonlinear process. Experimental metrology results confirm that these pulses exhibit amplitude squeezing, which is consistent with theoretical predictions. Moreover, we observe the temporal dynamics of amplitude uncertainty of the squeezed light, demonstrating that quantum uncertainty of light is controllable and tunable in real time. Additionally, we demonstrate control over the quantum state of light by switching between amplitude and phase squeezing. Our ability to generate and manipulate ultrafast, squeezed, synthesized light waveforms with attosecond resolution unlocks exciting possibilities for quantum technologies, including petahertz-scale secure quantum communication, quantum computing, and ultrafast spectroscopy. As an example, we introduce an attosecond quantum encryption protocol leveraging squeezed synthesized light for secure digital communication at unprecedented speeds. This work paves the way for exploring quantum uncertainty dynamics and establishes the foundation for the emerging ultrafast and attosecond quantum science fields.
Attosecond metrology is the ability to measure ultrafast optical light-wave oscillations, yet its approach has been limited to classical fields. Hence, the influence of the fluctuations of a quantum field on attosecond measurements has remained unexplored. Here, we close this gap by showing that the attosecond streaking measurement of bright quantum light is sensitive to quantum fluctuations of the optical field on the attosecond timescale. The distinct sub-cycle modulations allow to extract the properties of the squeezed field quadrature in regimes where conventional state tomography approaches reach their limitation. With the full quantum optical attosecond streaking scheme developed here, we provide a certification method that can measure quantum squeezing below the shot noise limit, thereby overcoming the problem of tomographically measuring bright quantum light. This opens the way towards quantum optical metrology of field fluctuations with attosecond temporal resolution.