We demonstrate simultaneous phase and amplitude imaging of cold atoms using an intrinsically stable interferometer based on polarization beam-displacers. This method allows for the straight-forward retrieval of absorption and phase-shift experienced by an optical probe transmitted through an atomic sample. Furthermore, we show that our technique has a signal-to-noise ratio limited only by photon shot-noise.
We demonstrate simultaneous phase and amplitude imaging of cold atoms using an intrinsically stable interferometer based on polarization beam-displacers. This method allows for the straight-forward retrieval of absorption and phase-shift experienced by an optical probe transmitted through an atomic sample. Furthermore, we show that our technique has a signal-to-noise ratio limited only by photon shot-noise.
We theoretically develop and experimentally demonstrate a holographic method for imaging cold atoms at the diffraction and photon shot noise limits. Aided by a double point source reference field, a simple iterative algorithm robustly removes the twin image of an 87 Rb cold atom sample during the image reconstruction. Shot-noise limited phase shift and absorption images are consistently retrieved at various probe detunings, and during the laser cooling process. We consistently resolve less than 2 mrad phase shift ( attenuation) of the probe light, outperforming shot-noise limited phase-contrast (absorption) imaging by a factor of 4 or more if the same camera is used without pixel saturation. We discuss the possible extension of this work for precise phase imaging of dense atomic gases, and for off-resonant probing of multiple atoms in optical lattices.
We propose a lens-free nondestructive imaging method for cold atomic clouds using a Gaussian beam accompanied with phase shifting interferometry. This scheme requires no imaging lens. Hence, aberrations associated with it are completely eliminated and mechanical focusing can be avoided. Compared with the common single-beam nondestructive means, our proposed scheme lowers the energy per probe pulse delivered to the cold samples by almost three orders of magnitude, due to signal enhancement inherently provided in the two-beam configuration. Moreover, higher image resolution is attainable by magnifying the far-field interference distribution using a divergent Gaussian beam. We examine this novel lensless detection means for in situ imaging on typical cold atomic clouds under experimentally achievable conditions. Our simulations show the cloud position can be precisely determined, depending upon the cloud size and probe parameters, with an uncertainty from a few hundreds of micrometers to only a few micrometers, and the spatial resolution of the retrieved phase image can reach the diffraction limit.
In our high-precision atom interferometer, the measured atomic phase shift is sensitive to rotations and accelerations of the apparatus, and also to phase fluctuations of the Raman lasers. In this paper we study two principal noise sources affecting the atomic phase shift, induced by optical phase noise and vibrations of the setup. Phase noise is reduced by carrying out a phase lock of the Raman lasers after the amplification stages. We also present a new scheme to reduce noise due to accelerations by using a feed-forward on the phase of the Raman beams. With these methods, it should be possible to reach the range of the atomic quantum projection noise limit, which is about 1 mrad rms for our experiment, i.e. 30 nrad s-1 Hz-1/2 for a rotation measurement.
Recovering both amplitude and phase information from a system is a fundamental goal of optical imaging. At the same time, it is crucial to operate at low photon doses to avoid altering the sample, particularly in biological applications. Quantum imaging provides a powerful route to extract more information per photon than classical techniques, which are ultimately limited by shot-noise. However, the trade-off between quantum noise reduction and spatial resolution has long been regarded as a major obstacle to the application of quantum techniques to small cellular and sub-cellular structures, where they could offer the greatest benefits. Here, we overcome this limitation by demonstrating sub-shot-noise quantitative phase imaging of biological cells based on the transport-of-intensity equation, enabling high-fidelity, label-free imaging of key cellular and sub-cellular features. We achieve high-resolution phase imaging limited only by the numerical aperture, while simultaneously obtaining a resolution-independent quantum advantage. Unlike other quantum imaging approaches, our method operates in a quasi-single-shot, wide-field configuration, retrieves both phase and amplitude information, and does not rely on interferometric measurements, making it intrinsically fast and stable. These results pave the way for the immediate application of sub-shot-noise imaging in biological microscopy.
We propose a scheme to engage phase shifting interferometry on cold atomic samples and present the simulation results under several experimentally achievable conditions nowadays. This method allows far-detuning, low power probing, and is intrinsically nondestructive. This novel detection means yields image quality superior to the conventional phase contrast imaging at certain conditions and could be experimentally realized. Furthermore, the longitudinal resolution of imaging by this manner is mainly set by optical interference and can be better than the diffraction limit. This scheme also provides special advantages to diagnose the surface-trapped clouds, with which phase imaging on the fabricated wires and atoms altogether is possible as well.
Recovering both amplitude and phase information from a system is a fundamental goal of optical imaging. At the same time, it is crucial to operate at low photon doses to avoid altering the sample, particularly in biological applications. Quantum imaging provides a powerful route to extract more information per photon than classical techniques, which are ultimately limited by shot-noise. However, the trade-off between quantum noise reduction and spatial resolution has long been regarded as a major obstacle to the application of quantum techniques to small cellular and sub-cellular structures, where they could offer the greatest benefits. Here, we overcome this limitation by demonstrating sub-shot-noise quantitative phase imaging of biological cells based on the transport-of-intensity equation, enabling high-fidelity, label-free imaging of key cellular and sub-cellular features. We achieve high-resolution phase imaging limited only by the numerical aperture, while simultaneously obtaining a resolution-independent quantum advantage. Unlike other quantum imaging approaches, our method operates in a quasi-single-shot, wide-field configuration, retrieves both phase and amplitude information, and does not rely on interferometric measurements, making it intrinsically fast and stable. These results pave the way for the immediate application of sub-shot-noise imaging in biological microscopy.