The Concept of a Quantum Edge Simulator: Edge Computing and Sensing in the Quantum Era.

Sensors, enabling observations across vast spatial, spectral, and temporal scales, are major data generators for information technology (IT). Processing, storing, and communicating this ever-growing amount of data pose challenges for the current IT infrastructure. Edge computing-an emerging paradigm to overcome the shortcomings of cloud-based computing-could address these challenges. Furthermore, emerging technologies such as quantum computing, quantum sensing, and quantum communications have the potential to fill the performance gaps left by their classical counterparts. Here, we present the concept of an edge quantum computing (EQC) simulator-a platform for designing the next generation of edge computing applications. An EQC simulator is envisioned to integrate elements from both quantum technologies and edge computing to allow studies of quantum edge applications. The presented concept is motivated by the increasing demand for more sensitive and precise sensors that can operate faster at lower power consumption, generating both larger and denser datasets. These demands may be fulfilled with edge quantum sensor networks. Envisioning the EQC era, we present our view on how such a scenario may be amenable to quantification and design. Given the cost and complexity of quantum systems, constructing physical prototypes to explore design and optimization spaces is not sustainable, necessitating EQC infrastructure and component simulators to aid in co-design. We discuss what such a simulator may entail and possible use cases that invoke quantum computing at the edge integrated with new sensor infrastructures.

Atomic resonant single-mode squeezed light from four-wave mixing through feedforward.

Squeezed states of light have received renewed attention due to their applicability to quantum-enhanced sensing. To take full advantage of their reduced noise properties to enhance atomic-based sensors, it is necessary to generate narrowband near or on atomic resonance single-mode squeezed states of light. We have previously generated bright two-mode squeezed states of light, or twin beams, that can be tuned to resonance with the D1 line of Rb87 with a non-degenerate four-wave-mixing process in a double-lambda configuration in a Rb85 vapor cell. Here, we report on the use of feedforward to transfer the amplitude quantum correlations present in the twin beams to a single beam for the generation of single-mode amplitude squeezed light. With this technique, we obtain a single-mode squeezed state with -2.9±0.1 dB of squeezing when tuned off resonance and -2.0±0.1 dB when tuned on resonance with the D1 F=2 to F'=2 transition of Rb87.

Generation of 87Rb resonant bright two-mode squeezed light with four-wave mixing.

Squeezed states of light have found their way into a number of applications in quantum-enhanced metrology due to their reduced noise properties. In order to extend such an enhancement to metrology experiments based on atomic ensembles, an efficient light-atom interaction is required. Thus, there is a particular interest in generating narrow-band squeezed light that is on atomic resonance. This will make it possible not only to enhance the sensitivity of atomic based sensors, but also to deterministically transfer quantum correlations between two distant atomic ensembles. We generate bright two-mode squeezed states of light, or twin beams, with a non-degenerate four-wave mixing (FWM) process in hot 85Rb in a double-lambda configuration. Given the proximity of the energy levels in the D1 line of 85Rb and 87Rb, we are able to operate the FWM in 85Rb in a regime that generates two-mode squeezed states in which both modes are simultaneously on resonance with transitions in the D1 line of 87Rb, one mode with the F = 2 to F' = 2 transition and the other one with the F = 1 to F' = 1 transition. For this configuration, we obtain an intensity difference squeezing level of 3.5 dB. Moreover, the intensity difference squeezing increases to -5.4 dB and -5.0 dB when only one of the modes of the squeezed state is resonant with the D1 F = 2 to F' =-2 or F = 1 to F' = 1 transition of 87Rb, respectively.

Experimental observation of quantum correlations in four-wave mixing with a conical pump.

Generation of multimode quantum states has drawn much attention recently due to its importance for both fundamental science and the future development of quantum technologies. Here, by using a four-wave mixing process with a conical pump beam, we have experimentally observed about -3.8 dB of intensity-difference squeezing between a single-axial probe beam and a conical conjugate beam. The multi-spatial-mode nature of the generated quantum-correlated beams has been shown by comparing the variation tendencies of the intensity-difference noise of the probe and conjugate beams under global attenuation and local cutting attenuation. Due to its compactness, phase-insensitive nature, and easy scalability, our scheme may find potential applications in quantum imaging, quantum information processing, and quantum metrology.

Information encoding in the spatial correlations of entangled twin beams.

The ability to use the temporal and spatial degrees of freedom of quantum states of light to encode and transmit information is crucial for a robust and efficient quantum network. In particular, the potential offered by the large dimensionality of the spatial degree of freedom remains unfulfilled, as the necessary level of control required to encode information remains elusive. We encode information in the distribution of the spatial correlations of entangled twin beams by taking advantage of their dependence on the angular spectrum of the pump needed for four-wave mixing. We show that the encoded information can only be extracted through joint spatial measurements of the twin beams and not through individual beam measurements and that the temporal quantum correlations are not modified. The ability to engineer the spatial properties of twin beams will enable high-capacity quantum networks and quantum-enhanced spatially resolved sensing and imaging.

Temporally multiplexed storage of images in a gradient echo memory.

We study the storage and retrieval of images in a hot atomic vapor using the gradient echo memory protocol. We demonstrate that this technique allows for the storage of multiple spatial modes. We study both spatial and temporal multiplexing by storing a sequence of two different images in the atomic vapor. The effect of atomic diffusion on the spatial resolution is discussed and characterized experimentally. For short storage time a normalized spatial cross-correlation between a retrieved image and its input of 88 % is reported.

Transmission estimation at the quantum Cramér-Rao bound with macroscopic quantum light.

The field of quantum metrology seeks to apply quantum techniques and/or resources to classical sensing approaches with the goal of enhancing the precision in the estimation of a parameter beyond what can be achieved with classical resources. Theoretically, the fundamental minimum uncertainty in the estimation of a parameter for a given probing state is bounded by the quantum Cramér-Rao bound. From a practical perspective, it is necessary to find physical measurements that can saturate this fundamental limit and to show experimentally that it is possible to perform measurements with the required precision to do so. Here we perform experiments that saturate the quantum Cramér-Rao bound for transmission estimation over a wide range of transmissions when probing the system under study with a continuous wave bright two-mode squeezed state. To properly take into account the imperfections in the generation of the quantum state, we extend our previous theoretical results to incorporate the measured properties of the generated quantum state. For our largest transmission level of 84%, we show a 62% reduction over the optimal classical protocol in the variance in transmission estimation when probing with a bright two-mode squeezed state with -8 dB of intensity-difference squeezing. Given that transmission estimation is an integral part of many sensing protocols, such as plasmonic sensing, spectroscopy, calibration of the quantum efficiency of detectors, etc., the results presented promise to have a significant impact on a number of applications in various fields of research.

Multi-spatial-mode single-beam quadrature squeezed states of light from four-wave mixing in hot rubidium vapor.

We present experimental results on the generation of multi-spatial-mode, single-beam, quadrature squeezed light using four-wave mixing in hot Rb vapor. Squeezing and phase-sensitive deamplification are observed over a range of powers and detunings near the (85)Rb D1 atomic transition. We observe -3 dB of vacuum quadrature squeezing, comparable to the best single-spatial mode results previously reported using atomic vapors, however, produced here in multiple spatial modes. We confirm that the squeezing is present in more than one transverse mode by studying the spatial distribution of the noise properties of the field.

Entangling light in its spatial degrees of freedom with four-wave mixing in an atomic vapor.

The entanglement properties of two beams of light can reside in subtle correlations that exist in the unavoidable quantum fluctuations of their amplitudes and phases. Recent advances in the generation of nonclassical light with four-wave mixing in an atomic vapor have permitted the production and the observation of entanglement that is localized in almost arbitrary transverse regions of a pair of beams. These multi-spatial-mode entangled beams may prove useful for an array of applications ranging from noise-free imaging and improved position sensing to quantum information processing.

Phase-locked laser system for use in atomic coherence experiments.

We describe a phase-coherent laser system designed for use in experiments involving coherently prepared atomic media. We implement a simple technique based on a sample-and-hold circuit together with a reset of the integrating electronics that makes it possible to scan continuously the relative frequency between the lasers of over tens of gigahertz while keeping them phase locked. The system consists of three external-cavity diode lasers operating around 795 nm. A low-power laser serves as a frequency reference for two high-power lasers which are phased locked with an optical phase-locked loop. We measured the residual phase noise of the system to be less than 0.04 rad(2). In order to show the application of the system towards atomic coherence experiments, we used it to implement electromagnetically induced transparency in a rubidium vapor cell and obtained a reduction in the absorption coefficient of 92%.

Entangled images from four-wave mixing.

Two beams of light can be quantum mechanically entangled through correlations of their phase and intensity fluctuations. For a pair of spatially extended image-carrying light fields, the concept of entanglement can be applied not only to the entire images but also to their smaller details. We used a spatially multimode amplifier based on four-wave mixing in a hot vapor to produce twin images that exhibit localized entanglement. The images can be bright fields that display position-dependent quantum noise reduction in their intensity difference or vacuum twin beams that are strongly entangled when projected onto a large range of different spatial modes. The high degree of spatial entanglement demonstrates that the system is an ideal source for parallel continuous-variable quantum information protocols.

Honeycomb pattern formation by laser-beam filamentation in atomic sodium vapor.

We have observed transverse pattern formation leading to highly regular structures in both the near and far fields when a near-resonant laser beam propagates without feedback through an atomic sodium vapor. One example is a regular far-field honeycomb pattern, which results from the transformation of the laser beam within the vapor into a stable three-lobed structure with a uniform phase distribution and highly correlated power fluctuations. The predictions of a theoretical model of the filamentation process are in good agreement with these observations.