arXiv subjects

Duncan England

Publications and source records attributed to Duncan England.

At least 37 records · Page 2Linked to original sources

arXiv2024

Toward deterministic sources: Photon generation in a fiber-cavity quantum memory

We demonstrate the generation of photons within a fiber-cavity quantum memory, followed by later on-demand readout. Signal photons are generated by spontaneous four-wave mixing in a fiber cavity comprising a birefringent fiber with dichroic reflective end facets. The detection of the partner herald photon indicates the creation of the stored signal photon. After a delay, the signal photon is switched out of resonance with the fiber cavity by intracavity frequency translation using Bragg scattering four-wave mixing, driven by ancillary control pulses. We measure sub-Poissonian statistics in the output signal mode, with $g^{(2)}_{AC}=0.54(1)$ in the first readout bin and a readout frequency translation efficiency of $\approx$80%. The 1/e memory lifetime is $\approx$67 cavity cycles, or 1.68$μ$s. In an alternate fiber cavity, we show a strategy for noise reduction and measure $g^{(2)}_{AC}=0.068(10)$ after one cavity cycle.

quant-ph↗

arXiv2023

Intensity correlation holography for remote phase sensing and 3D imaging

Holography is an established technique for measuring the wavefront of optical signals through interferometric combination with a reference wave. Conventionally the integration time of a hologram is limited by the interferometer coherence time, thus making it challenging to prepare holograms of remote objects, especially using weak illumination. Here, we circumvent this limitation by using intensity correlation interferometry. Although the exposure time of individual holograms must be shorter than the interferometer coherence time, we show that any number of randomly phase-shifted holograms can be combined into a single intensity-correlation hologram. In a proof-of-principle experiment, we use this technique to perform phase imaging and 3D reconstruction of an object at a ~3m distance using weak illumination and without active phase stabilization.

physics.optics↗

arXiv2023

Ultrafast Measurement of Energy-Time Entanglement with an Optical Kerr Shutter

Recent experimental progress in quantum optics has enabled measurement of single photons on ultrafast timescales, beyond the resolution limit of single photon detectors. The energy-time degree of freedom has emerged as a promising avenue for quantum technologies, as entanglement between the frequency and temporal properties of two photons can be fully explored and utilized. Here, we implement optical Kerr shutters in single mode fibers to map out the sub-picosecond correlations of energy-time entangled photon pairs. These measurements, in addition to joint spectral measurements of the photon pair state, are used to verify entanglement by means of the violation of a time-bandwidth inequality.

quant-ph↗

arXiv2023

Quantum correlation light-field microscope with extreme depth of field

Light-field microscopy (LFM) is a 3D microscopy technique whereby volumetric information of a sample is gained by simultaneously capturing both the position and momentum (angular) information of light illuminating a scene. Conventional LFM designs generally require a trade-off between position and momentum resolution, requiring one to sacrifice resolving power for increased depth of field (DOF) or vice versa. In this work, we demonstrate a LFM design that does not require this trade-off by utilizing the inherent correlations between spatial-temporal entangled photon pairs. Here, one photon from the pair is used to illuminate a sample from which the position information of the photon is captured directly by a camera. By virtue of the strong momentum anti-correlation between the two photons, the momentum information of the illumination photon can then be inferred by measuring the angle of its entangled partner on a different camera. By using a combination of ray-tracing and a Gerchberg-Saxton type algorithm for the light field reconstruction, we demonstrate that a resolving power of 5 $μ$m can be maintained with a DOF of $\sim500$ $μ$m, approximately 3 times of the latest LFM designs or $>100$ time that of a conventional microscope. In the extreme, at a resolving power of 100 $μ$m, it is possible to achieve near infinite DOF.

quant-ph↗

arXiv2023

Measuring ultrafast time-bin qudits

Time-bin qudits have emerged as a promising encoding platform in many quantum photonic applications. However, the requirement for efficient single-shot measurement of time-bin qudits instead of reconstructive detection has restricted their widespread use in experiments. Here, we propose an efficient method to measure arbitrary superposition states of time-bin qudits and confirm it up to dimension 4. This method is based on encoding time bins at the picosecond time scale, also known as ultrafast time bins. By doing so, we enable the use of robust and phase-stable single spatial mode temporal interferometers to measure time-bin qudit in different measurement bases.

quant-ph↗

arXiv2022

Reconfigurable phase contrast microscopy with correlated photon pairs

A phase-sensitive microscopy technique is proposed and demonstrated that employs the momentum correlations inherent in spontaneous parametric down-conversion. One photon from a correlated pair is focused onto a microscopic target while the other is measured in the Fourier plane. This provides knowledge of the position and angle of illumination for every photon striking the target, allowing full post-production control of the illumination angle used to form an image. The versatility of this approach is showcased with asymmetric illumination and differential phase contrast imaging, without any beam blocks or moving parts.

quant-ph↗

arXiv2022

Characterisation of a single photon event camera for quantum imaging

We show a simple yet effective method that can be used to characterize the per pixel quantum efficiency and temporal resolution of a single photon event camera for quantum imaging applications. Utilizing photon pairs generated through spontaneous parametric down-conversion, the detection efficiency of each pixel, and the temporal resolution of the system, are extracted through coincidence measurements. We use this method to evaluate the TPX3CAM, with appended image intensifier, and measure an average efficiency of 7.4% and a temporal resolution of 7.3ns. Furthermore, this technique reveals important error mechanisms that can occur in post-processing. We expect that this technique, and elements therein, will be useful to characterise other quantum imaging systems.

quant-ph↗

arXiv2022

Snapshot hyperspectral imaging with quantum correlated photons

Hyperspectral imaging (HSI) has a wide range of applications from environmental monitoring to biotechnology. Current snapshot HSI techniques all require a trade-off between spatial and spectral resolution and are thus unable to achieve high resolutions in both simultaneously. Additionally, the techniques are resource inefficient with most of the photons lost through spectral filtering. Here, we demonstrate a snapshot HSI technique utilizing the strong spectro-temporal correlations inherent in entangled photons using a modified quantum ghost spectroscopy system, where the target is directly imaged with one photon and the spectral information gained through ghost spectroscopy from the partner photon. As only a few rows of pixels near the edge of the camera are used for the spectrometer, almost no spatial resolution is sacrificed for spectral. Also since no spectral filtering is required, all photons contribute to the HSI process making the technique much more resource efficient.

physics.optics↗

arXiv2022

Toward a Quantum Memory in a Fiber Cavity Controlled by Intracavity Frequency Translation

We propose a quantum memory protocol based on trapping photons in a fiber-integrated cavity, comprised of a birefringent fiber with dichroic reflective end facets. Photons are switched into resonance with the fiber cavity by intracavity Bragg-scattering frequency translation, driven by ancillary control pulses. After the storage delay, photons are switched out of resonance with the cavity, again by intracavity frequency translation. We demonstrate storage of quantum-level THz-bandwidth coherent states for a lifetime up to 16 cavity round trips, or 200ns, and a maximum overall efficiency of 73%.

quant-ph↗

arXiv2021

Ray-tracing with quantum correlated photons to image a 3D scene

To capture the 3D information of a scene, conventional techniques often require multiple 2D images of the scene to be captured from different perspectives. In this work we demonstrate the reconstruction of a scene's 3D information through ray-tracing using quantum correlated photon pairs. By capturing the two photons in different image planes using time-tagging cameras and taking advantage of the position, momentum and time correlation of the photons, the photons' propagation trajectory can be reconstructed. With this information on every photon pair, we were able to demonstrate refocusing, depth of field adjustment and parallax visualization of a 3D scene. With future camera advancements, this technique could achieve a much higher momentum resolution than conventional techniques thus giving larger depth of field and more viewing angles. The high photon correlation and low photon flux from a quantum source also makes the technique well suited for 3D imaging of light sensitive samples.

quant-ph↗

arXiv2021

High Speed Imaging of Spectral-Temporal Correlations in Hong-Ou-Mandel Interference

In this work we demonstrate spectral-temporal correlation measurements of the Hong-Ou-Mandel (HOM) interference effect with the use of a spectrometer based on a photon-counting camera. This setup allows us to take, within seconds, spectral temporal correlation measurements on entangled photon sources with sub-nanometer spectral resolution and nanosecond timing resolution. Through post processing, we can observe the HOM behaviour for any number of spectral filters of any shape and width at any wavelength over the observable spectral range. Our setup also offers great versatility in that it is capable of operating at a wide spectral range from the visible to the near infrared and does not require a pulsed pump laser for timing purposes. This work offers the ability to gain large amounts of spectral and temporal information from a HOM interferometer quickly and efficiently and will be a very useful tool for many quantum technology applications and fundamental quantum optics research.

physics.optics↗

arXiv2021

Quantum communication with ultrafast time-bin qubits

The photonic temporal degree of freedom is one of the most promising platforms for quantum communication over fiber networks and free-space channels. In particular, time-bin states of photons are robust to environmental disturbances, support high-rate communication, and can be used in high-dimensional schemes. However, the detection of photonic time-bin states remains a challenging task, particularly for the case of photons that are in a superposition of different time-bins. Here, we experimentally demonstrate the feasibility of picosecond time-bin states of light, known as ultrafast time-bins, for applications in quantum communications. With the ability to measure time-bin superpositions with excellent phase stability, we enable the use of temporal states in efficient quantum key distribution protocols such as the BB84 protocol.

quant-ph↗

arXiv2021

Achieving ultimate noise tolerance in quantum communication

At the fundamental level, quantum communication is ultimately limited by noise. For instance, quantum signals cannot be amplified without the introduction of noise in the amplified states. Furthermore, photon loss reduces the signal-to-noise ratio, accentuating the effect of noise. Thus, most of the efforts in quantum communications have been directed towards overcoming noise to achieve longer communication distances, larger secret key rates, or to operate in noisier environmental conditions. Here, we propose and experimentally demonstrate a platform for quantum communication based on ultrafast optical techniques. In particular, our scheme enables the experimental realization of high-rates and quantum signal filtering approaching a single spectro-temporal mode, resulting in a dramatic reduction in channel noise. By experimentally realizing a 1-ps optically induced temporal gate, we show that ultrafast time filtering can result in an improvement in noise tolerance by a factor of up to 1200 compared to a 2-ns electronic filter enabling daytime quantum key distribution or quantum communication in bright fibers.

quant-ph↗

arXiv2020

Quantum-Assisted Optical Interferometers: Instrument Requirements

It has been recently suggested that optical interferometers may not require a phase-stable optical link between the stations if instead sources of quantum-mechanically entangled pairs could be provided to them, enabling extra-long baselines and benefiting numerous topics in astrophysics and cosmology. We developed a new variation of this idea, proposing that photons from two different sources could be interfered at two decoupled stations, requiring only a slow classical connection between them. We show that this approach could allow high-precision measurements of the relative astrometry of the two sources, with a simple estimate giving angular resolution of $10 \ μ$as in a few hours' observation of two bright stars. We also give requirements on the instrument for these observations, in particular on its temporal and spectral resolution. Finally, we discuss possible technologies for the instrument implementation and first proof-of-principle experiments.

astro-ph.IM↗

arXiv2020

Multivariate Discrimination in Quantum Target Detection

We describe a simple multivariate technique of likelihood ratios for improved discrimination of signal and background in multi-dimensional quantum target detection. The technique combines two independent variables, time difference and summed energy, of a photon pair from the spontaneous parametric down-conversion source into an optimal discriminant. The discriminant performance was studied in experimental data and in Monte-Carlo modelling with clear improvement shown compared to previous techniques. As novel detectors become available, we expect this type of multivariate analysis to become increasingly important in multi-dimensional quantum optics.

quant-ph↗

arXiv2020

Enhancing LIDAR performance metrics using continuous-wave photon-pair sources

In order to enhance LIDAR performance metrics such as target detection sensitivity, noise resilience and ranging accuracy, we exploit the strong temporal correlation within the photon pairs generated in continuous-wave pumped semiconductor waveguides. The enhancement attained through the use of such non-classical sources is measured and compared to a corresponding target detection scheme based on simple photon-counting detection. The performances of both schemes are quantified by the estimation uncertainty and Fisher information of the probe photon transmission, which is a widely adopted sensing figure of merit. The target detection experiments are conducted with high probe channel loss ($\simeq 1-5\times10^{-5}$) and formidable environment noise up to 36 dB stronger than the detected probe power of $1.64\times 10^{-5}$ pW. The experimental result shows significant advantages offered by the enhanced scheme with up to 26.3 dB higher performance in terms of estimation uncertainty, which is equivalent to a reduction of target detection time by a factor of 430 or 146 (21.6 dB) times more resilience to noise. We also experimentally demonstrated ranging with these non-classical photon pairs generated with continuous-wave pump in the presence of strong noise and loss, achieving $\approx$5 cm distance resolution that is limited by the temporal resolution of the detectors.

physics.optics↗

arXiv2020

Underwater quantum communication over a 30-meter flume tank

Underwater quantum communication has recently been explored using polarization and orbital angular momentum. Here, we show that spatially structured modes, e.g., a coherent superposition of beams carrying both polarization and orbital angular momentum, can also be used for underwater quantum cryptography. We also use the polarization degree of freedom for quantum communication in an underwater channel having various lengths, up to $30$ meters. The underwater channel proves to be a difficult environment for establishing quantum communication as underwater optical turbulence results in significant beam wandering and distortions. However, the errors associated to the turbulence do not result in error rates above the threshold for establishing a positive key in a quantum communication link with both the polarization and spatially structured photons. The impact of the underwater channel on the spatially structured modes is also investigated at different distances using polarization tomography.

quant-ph↗

arXiv2020

Multidimensional quantum-enhanced target detection via spectro-temporal correlation measurements

In this work we investigate quantum-enhanced target detection in the presence of large background noise using multidimensional quantum correlations between photon pairs generated through spontaneous parametric down-conversion. Until now similar experiments have only utilized one of the photon pairs' many degrees of freedom such as temporal correlations and photon number correlations. Here, we utilized both temporal and spectral correlations of the photon pairs and achieved over an order of magnitude reduction to the background noise and in turn significant reduction to data acquisition time when compared to utilizing only temporal modes. We believe this work represents an important step in realizing a practical, real-time quantum-enhanced target detection system. The demonstrated technique will also be of importance in many other quantum sensing applications and quantum communications.

quant-ph↗