Xiaolong Su

As a powerful tool of biological imaging, stimulated Raman scattering (SRS) microscopy enables rapid, label-free imaging with high molecular specificity. In the application of SRS microscopy, it is essential to break the optical diffraction limit and enhance the resolution. Here, we demonstrate an effective method that combines antiphase demodulation with a deconvolution algorithm to achieve super-resolution SRS imaging. By introducing a donut-shaped pump beam with antiphase modulation in SRS microscopy, the signal around the focal center is effectively suppressed, enabling subdiffraction-limited imaging. Followed by a deconvolution algorithm, we obtain a 3.5-fold improvement in spatial resolution using human hair as a test specimen. The result offers a practical method for super-resolution SRS microscopy without significant sample damage, broadening applications in super-resolution, label-free biological imaging.

The development of large-scale, high-fidelity quantum processors is a fundamental scientific challenge, essential for exploring the boundaries of classical computation and advancing towards fault-tolerant systems. Gaussian boson sampling not only serves as a prominent model for demonstrating quantum computational advantage^1,2,3 but can also generate bosonic error-correcting codes for fault-tolerant quantum computing^4,5,6. However, its scalability has been hindered by significant photon loss in increasingly large and complex encoding circuits. Here we show a programmable photonic quantum processor, Jiuzhang 4.0, which incorporates 1,024 high-efficiency squeezed states into a hybrid spatial–temporal encoded 8,176-mode circuit. By achieving 92% source efficiency and 51% overall system efficiency, the processor produces samples with detection events up to 3,050 photons, representing an order-of-magnitude increase in scale over previous demonstrations^7,8,9,10. This architecture realizes a cubic scaling of connectivity (16³ = 4, 096), enabling sampling within a Hilbert space of dimension approximately 10^2,461. The experimental results are rigorously validated against all current classical simulation methods, especially the matrix product state algorithms recently designed to exploit photon loss¹¹. The ability to control thousands of photons in programmable low-loss quantum processors pushes the experimental frontier into a regime far beyond classical tractability and opens a pathway to trillion-qumode three-dimensional cluster states and fault-tolerant photonic quantum hardware.

Achieving high end-to-end efficiency and broadband quantum memory of squeezed light is crucial for continuous-variable quantum information processing. Existing demonstrations fail to store squeezed states across their full squeezing bandwidth. Here, we present a full-bandwidth quantum memory of squeezed light with up to 24 MHz bandwidth, which is at least 12 times that of previous narrowband resonant memory systems, via a far-off resonant Raman process. We achieve output squeezing as high as 1.0±0.29dB, with fidelity above 92±0.5% and a memory efficiency of 80%, corresponding to an end-to-end efficiency of 64.2±0.7% when input squeezing is 1.6±0.23dB. The lowest excess noise of 0.025 shot-noise unit in the memory system is estimated by the noisy model, which benefits from optimizing quantum memory performance with a backward-retrieval strategy. Our results show high-performance memory for squeezed states within tens of MHz-level bandwidth, which has potential applications in high-speed quantum information processing.

A squeezed state is a key quantum resource for quantum information processing and quantum metrology. It is essential to extend the dimension of the squeezed state for spatially multiplexed large-capacity quantum communication and quantum precision measurements. Here, we report the experimental preparation of a picosecond pulsed squeezed state carrying orbital angular momentum (OAM). By modulating bright pulsed squeezed light with a spatial light modulator, we generate a squeezed state with Laguerre-Gaussian distribution, whose topological charges are up to l = 20 and squeezed noise is 1.22 dB below the shot noise level. The presented bright picosecond pulsed squeezed light carrying high-order OAM provides promising resources for high-dimensional quantum information processing.

In addition to carrying spin angular momentum (SAM), light can also possess orbital angular momentum (OAM), whose quantum number can, in principle, take any integer value. This property provides a new degree of freedom to expand the capacity of both classical and quantum information. In recent years, generating OAM multiplexed continuous-variable entanglement via four-wave mixing (FWM) has emerged as an effective approach to increasing the capacity of quantum information channels. Consequently, there is a growing demand for precise characterization of the OAM spectrum in such quantum beams. Here we present, to the best of our knowledge, the first experimental demonstration of OAM spectrum measurement in quantum optics using phase-shifting interferometry (PSI). This method enables accurate characterization of the OAM spectrum of both the probe and conjugate beams in OAM multiplexed continuous-variable entanglement generated via the FWM process. These results provide an experimental foundation for the reliable detection and utilization of multiplexed OAM degrees of freedom in quantum communication and quantum information processing.

Entanglement-assisted quantum communication has substantial advantages in surpassing the power of classical communication by utilizing the entangled state. Up to now, most of entanglement-assisted quantum communications with dense coding are limited to the proof-of-principle experiments. Here, we experimentally demonstrate the deterministic entanglement-assisted quantum communication based on the continuous-variable (CV) entangled state over 20 km commercial fiber channels. We propose a new CV dense coding scheme with improved classical signals and show that the transmission distance of CV entanglement-assisted quantum communication can be extended compared with that using fixed classical signals. By applying the frequency division multiplexing technique, we simultaneously decode 10 classical signals submerged in the shot noise of coherent state with the help of CV entangled state after the transmission through a 20.121 km fiber channel. The results show that around 3 times of channel capacity in classical communication with coherent state are achieved in the CV entanglement-assisted communication with the frequency division multiplexing technique. Our result takes a crucial step towards realizing the deterministic metropolitan entanglement-assisted quantum communication in practical quantum channels.

The pulsed squeezed state plays a pivotal role in quantum information processing and precision measurement. In the detection of the pulsed squeezed state, the high noise power at its repetition rate prevents the achievement of a high signal-to-noise ratio (SNR). Therefore, a high-SNR detector that can suppress the high noise power of the repetition rate of pulsed light is very crucial. In this paper, we present a high-SNR resonant balanced photodetector that filters out the noise power of the repetition rate by introducing an LC series notch filter. A 24.37 dB attenuation is obtained at the 80 MHz repetition rate by finely adjusting the capacitance of the LC series notch filter. Consequently, the photodetector’s maximum SNR is improved to 19.60 dB, which is 5 dB higher than previous studies. Our work provides a key detection tool for the measurement of the pulsed squeezed state.