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Publications (271)
We present a simple way to enhance bidirectional broadband modulation in a traveling wave Mach–Zehnder electro-optic modulator (EOM) by removing matched impedance and effecting a reflection of the microwave signal. A model was devised for determining the modulation efficiency (ME) in the presence of microwave reflection, without access to the physi...
Measurement-device-independent quantum key distribution (MDI-QKD) closes all the security loopholes in the detection system and is a promising solution for secret key sharing. Polarization encoding is the most common QKD encoding scheme, as it is straightforward to prepare and measure. However, implementing polarization encoding in MDI QKD imposes...
Quantum information is often carried in the frequency and polarization degrees of freedom (DoFs) in single photons and entangled photons. We demonstrate an approach to couple and decouple the frequency and polarization DoFs of broadband biphotons. Our approach is based on a nonlinear interferometer consisting of a linear dispersive medium and a pol...
We demonstrate a low-cost, fiber-based, pulsed entanglement source, using periodically-poled silica fiber and a pulsed 780nm diode laser, which generates ~1ns pulses of polarization-entangled photon pairs at up to 60MHz, 0.15 pairs/pulse.
In this work, we propose an improved method of training linear support vector machines (SVMs) to generate entanglement witnesses for systems of 3, 4, and 5 qubits. SVMs generate hyperplanes represented by a weighted sum of expectation values of local observables, whose coefficients are optimized to provide a positive sum for all separable states an...
In this work, we show a correspondence between linear support vector machines (SVMs) and entanglement witnesses, and use this correspondence to generate entanglement witnesses for bipartite and tripartite qubit (and qudit) target entangled states. An SVM allows for the construction of a hyperplane that clearly delineates between separable states an...
We implemented MDI-QKD with a novel polarization compensation scheme using discarded bits without reducing the key-sharing cycle or demanding additional resources. Polarization drift was maintained below 0.13 rad over a 40 km unisolated fibre spool for four hours, and the average secret key rate generated was 7.45 × 10 ⁻ ⁶ bits per pulse.
We show the Sum-Frequency Generation characteristics of our periodically-poled silica fiber source for spontaneous parametric downconversion at 780 and 1560 nm; efficiencies are on an order of 4 × 10 ⁻⁶ and photon bandwidths of ~489 GHz.
We use the interplay between polarization-dependent gain and frequency-dependent po-larization eigenmodes of a twisted (elliptically-birefringent) medium and demonstrate a tunable sub-megahertz optical feature at room temperature without resonators or loss.
Electro-optic phase modulators are commonly used for polarization and phase encoding in quantum key distribution. Here, a novel state preparation flaw which arises during high speed electro-optic phase modulation is identified and characterized. The impact of this state preparation flaw on the secure key rate is quantified.
We find that our W state witnesses derived with a Support Vector Machine have comparable noise tolerance while requiring fewer measurements than the fidelity method; this result is physically verified on an IBM Quantum Processor.
Entanglement distillation has many applications in quantum information processing and is an important tool for improving the quality and efficiency of quantum communication, cryptography, computing, and simulation. We propose an entanglement distillation scheme using only one pair of polarization-frequency hyperentangled photons, which can be equiv...
While measurement-device-independent (MDI) quantum key distribution (QKD) allows two trusted parties to establish a shared secret key from a distance without needing to trust a central detection node, their quantum sources must be well characterized, with side channels at the source posing the greatest loophole to the protocol's security. In this p...
Measurement-device-independent quantum key distribution (MDI-QKD) closes all the security loopholes in the detection system and is a promising solution for secret key sharing. Polarization encoding is the most common QKD encoding scheme, as it is straightforward to prepare and measure. However, implementing polarization encoding in MDI QKD imposes...
Ultra-narrow optical spectral features resulting from highly dispersive light–matter interactions are essential for a broad range of applications such as spectroscopy, slow-light and high-precision sensing. Features approaching sub-megahertz or, equivalently, Q-factors up to one billion and beyond, are challenging to obtain in solid-state systems,...
Hyperentanglement, the simultaneous and independent entanglement of quantum particles in multiple degrees of freedom, is a powerful resource that can be harnessed for efficient quantum information processing. In photonic systems, the two degrees of freedom (DOFs) often used to carry quantum and classical information are polarization and frequency,...
Hyperentanglement, the simultaneous and independent entanglement of quantum particles in multiple degrees of freedom, is a powerful resource that can be harnessed for efficient quantum information processing. In photonic systems, the two degrees of freedom (DOFs) often used to carry quantum and classical information are polarization and frequency,...
Twin-field quantum key distribution (TFQKD) systems have shown great promise for implementing practical long-distance secure quantum communication due to its measurement-device-independent nature and its ability to offer fundamentally superior rate-loss scaling than point-to-point QKD systems. A surge of research and development effort in the last...
We experimentally demonstrate the generation of telecom-band biphotons hyperentangled in both the polarization and frequency DoFs using a periodically-poled silica fiber and observe entanglement concurrences above 0.95 for both DOFs.
Hyperentanglement, the simultaneous and independent entanglement of quantum particles in multiple degrees of freedom, is a powerful resource that can be harnessed for efficient quantum information processing. In photonic systems, the two degrees of freedom (DoF) often used to carry quantum and classical information are polarization and frequency, t...
Twin-field (TF) quantum key distribution (QKD) is highly attractive because it can beat the fundamental limit of secret key rate for point-to-point QKD without quantum repeaters. Many theoretical and experimental studies have shown the superiority of TFQKD in long-distance communication. All previous experimental implementations of TFQKD have been...
Despite tremendous theoretical and experimental progress in continuous variable (CV) quantum key distribution (QKD), the security has not been rigorously established for most current continuous variable quantum key distribution systems that have imperfections. Among these imperfections, intensity fluctuation is one of the principal problems affecti...
While measurement-device-independent (MDI) quantum key distribution (QKD) allows two trusted parties to establish a shared secret key from a distance without needing to trust a central detection node, their quantum sources must be well-characterized, with side-channels at the source posing the greatest loophole to the protocol's security. In this p...
Quantum communication complexity explores the minimum amount of communication required to achieve certain tasks using quantum states. One representative example is quantum fingerprinting, in which the minimum amount of communication could be exponentially smaller than the classical fingerprinting. Here, we propose a quantum fingerprinting protocol...
Integrated photonic sensors can provide large scale, flexible detection schemes. Photonic crystal slabs (PCSs) offer a miniaturized platform for wideband, sensitive ultrasound detection by exploiting the photoelastic effect in water. However, poor modal overlap with the sensing medium and non-negligible absorption loss of the aqueous medium have pr...
In this work, we show a correspondence between linear support vector machines (SVMs) and entanglement witnesses, and use this correspondence to generate entanglement witnesses for bipartite and tripartite qubit (and qudit) target entangled states. An SVM allows for the construction of a hyperplane that clearly delineates between separable states an...
Twin-field quantum key distribution (TFQKD) systems have shown great promise for implementing practical long-distance secure quantum communication due to its measurement-device-independent nature and its ability to offer fundamentally superior rate-loss scaling than point-to-point QKD systems. A surge of research and development effort in the last...
Integrated photonic sensors can provide large scale, flexible detection schemes. Photonic crystal slabs (PCS) offer a miniaturized platform for wideband, sensitive ultrasound detection by exploiting the photoelastic effect in water. However, poor modal overlap with the sensing medium and non-negligible absorption loss of the aqueous medium have pre...
Ultra-narrow optical spectral features have broad applications in spectroscopy, slow light, and sensing. Features approaching sub-MHz, or equivalently, Q-factors approaching 1 billion and beyond, are challenging to obtain in solid-state systems, ultimately limited by loss. We present a new paradigm to achieve tunable sub-MHz spectral features at ro...
Ultra-narrow optical spectral features have broad applications in spectroscopy, slow light, and sensing. Features approaching sub-MHz, or equivalently, Q-factors approaching 1 billion and beyond, are challenging to obtain in solid-state systems, ultimately limited by loss. We present a new paradigm to achieve tunable sub-MHz spectral features at ro...
Ultra-narrow spectral features are desirable for a broad range of applications, from precision spectroscopy to atomic clocks to slow-light and microwave photonics, and are conventionally realized using either ultrahigh-Q resonant structures or atomic resonances. Ultrahigh-Q structure often involves microfabrication, and suffers from loss mechanisms...
Ultra-narrow spectral features are desirable for a broad range of applications, and they are conventionally realized using ultrahigh Q resonant structures. These structures typically require precision fabrication processes, and moreover, since they are passive, they suffer from signal attenuation. Here, we demonstrate a novel way to achieve sub-MHz...
In this Letter, we report a polarization-entangled photon-pair source based on type-II spontaneous parametric downconversion at telecom O-band in periodically poled silica fiber (PPSF). The photon-pair source exhibits more than 130 nm ( ${\sim}24\;{\rm THz}$ ∼ 24 T H z ) emission bandwidth centered at 1306.6 nm. The broad emission spectrum results...
In this letter, we report a polarization-entangled photon-pair source based on type-II spontaneous parametric down conversion at telecom O-band in periodically poled silica fiber (PPSF). The photon-pair source exhibits more than 130 nm (~24 THz) emission bandwidth centered at 1306.6 nm. The broad emission spectrum results in a short biphoton correl...
We demonstrate a correspondence between linear support vector machines (SVM) and entanglement witnesses, and use this correspondence to generate entanglement witnesses for bipartite qubit, tripartite qubit, and bipartite qutrit systems.
We propose a signal patterning technique to mitigate backscattering and optimize secure key rates for Sagnac twin-field QKD systems. Simulation results based on experimentally-measured backscattering coefficient yield positive key rates for 250km using APD detectors.
We propose and implement a novel polarization compensation in MDI-QKD systems using discarded bits, without reducing key-sharing cycle or demanding additional resources. Polarization drift is maintained below 0.15 rad over 40 km of fibre.
We report a method of generating an ultra-narrow tunable spectral dip with a bandwidth of ∼ 1 MHz in a resonator-free arrangement by using stimulated Brillouin scattering in a spun birefringent fiber.
Time-dependent side channels pose a security risk for quantum key distribution (QKD). We apply a numerical security proof technique to study such a side-channel, which we identify in a common source implementation for measurement-device-independent QKD employing Faraday mirrors.
We demonstrate a novel resonator-free approach to realize tunable, sub-MHz features by exploiting gain-enhanced polarization pulling in a spun fiber. A 0.72 MHz dip is experimentally achieved, equivalent to a Q-factor approaching 1 billion.
Despite tremendous theoretical and experimental progress in continuous variable (CV) quantum key distribution (QKD), its security has not been rigorously established for practical systems with multiple imperfections. The idea of tagging is widely used in security proofs of discrete variable quantum key distribution with imperfect devices. In this p...
This paper proposes a novel iteration Bayesian reweighed (IBR) algorithm to obtain accurate estimates of a measurement parameter that uses only a few noisy measurement data. The method is applied to optimize the frequency fluctuation in an optical carrier-based microwave interferometry (OCMI) system. The algorithm iteratively estimates the frequenc...
Quantum communication complexity studies the efficiency of information communication (that is, the minimum amount of communication required to achieve a certain task) using quantum states. One representative example is quantum fingerprinting, in which the simultaneous message passing model is considered and the minimum amount of communication could...
Dispersion plays a major role in the behavior of light inside photonic devices. Current state-of-the-art dispersion measurement techniques utilize linear interferometers that can be applied to devices with small dispersion-length products. However, linear interferometry often requires beam alignment and phase stabilization. Recently, common-path no...
Exploiting the simultaneous entanglement (hyperentanglement) in multiple degrees of freedom of an entangled photon pair increases the dimensionality of the Hilbert space for quantum information processing. However, the generation of hyperentangled photon pairs collinearly, while capable of high brightness, results in a smaller Hilbert space due to...
Twin-field (TF) quantum key distribution (QKD) is highly attractive because it can beat the fundamental limit of secret key rate for point-to-point QKD without quantum repeaters. Many theoretical and experimental studies have shown the superiority of TFQKD in long-distance communication. All previous experimental implementations of TFQKD have been...
We generate biphotons with degree of polarisation entanglement that varies over a concurrence range 0.12 < C < 0.97, depending on the frequency of biphotons. Our interferometric scheme offers a convenient means towards the generation of arbitrary biphoton states.
We demonstrate a first experiment of twin-field quantum key distribution over asymmetric channels. We use asymmetric signal intensities and show that the secret key rate can beat the repeaterless bound at 50 (30+20) dB total loss.
We exploit the refractive-index (RI)-sensing capabilities of a photonic crystal slab (PCS) and the photoelastic effect in a polymer overlayer to measure ultrasonic signals in water. Using a TM resonance in the PCS device, we obtain an acoustic sensitivity of 4.4×10−2 nm/MPa.
We present a novel dispersion measurement technique using a reflective commonpath nonlinear interferometer. Our method is fast, alignment-free, and does not require phasestabilization. It can extract the dispersion for samples with dispersion-length products as small as D × L ~0:007 ps/nm.
We train a neural network to predict the optical properties (center wavelength λ 0 , linewidth, sensitivity S ) of photonic crystal slab structures. We are able to faithfully model the results to within 1% for λ 0 and S .
Exploiting hyperentanglement of photon pairs, that is, simultaneous entanglement in multiple degrees of freedom(DOFs), increases the dimensionality of Hilbert spaces for quantum information processing. However, generation of hyperentangled photon pairs collinearlly, while produces high brightness, results in a smaller Hilbert space due to the two p...
We propose and demonstrate a multichannel spatial-domain fiber cavity ringdown (FCRD) pressure sensing scheme based on frequency-shifted interferometry (FSI). In contrast to existing multichannel FCRD techniques, multichannel FSI-FCRD measures intensity decay rates of continuous-wave (CW) light from different fiber ringdown cavities (RDCs) in the s...
![Fidelity, concurrence, and purity [Tr(^ ρ 2 )] of the biphoton state...](publication/335723422/figure/tbl1/AS:801572170764288@1568121106206/Fidelity-concurrence-and-purity-Tr-r-2-of-the-biphoton-state-measured-in_Q320.jpg)
Quantum entanglement is an integral part of quantum optics and has been exploited in areas such as computation, cryptography and metrology. The entanglement between photons can be present in various degrees of freedom (DOFs), and even the simplest bi-partite systems can occupy a large Hilbert space. Therefore, it is desirable to exploit this multi-...
Quantum entanglement is an integral part of quantum optics and has been exploited in areas such as computation, cryptography and metrology. The entanglement between photons can be present in various degrees of freedom (DOFs), and even the simplest bi-partite systems can occupy a large Hilbert space. Therefore, it is desirable to exploit this multi-...
The twin-field (TF) quantum key distribution (QKD) protocol and its variants are highly attractive because they can beat the well-known fundamental limit of the secret key rate for point-to-point QKD without quantum repeaters (repeaterless bound). In this Letter, we perform a proof-of-principle experimental demonstration of TFQKD based on the proto...
Quantum Key Distribution (QKD) in principle offers unconditional security based on the laws of physics. Continuous variable (CV) quantum key distribution has the potential for high-key-rate and low-cost implementations using standard telecom components. Despite tremendous theoretical and experimental progress in continuous-variable quantum key dist...
The thermal stability of drawing-tower grating (DTG) has become the primary concern in applications because of its great advantages in building a large-capacity distributed fiber grating sensing network. Different aging trainings were performed on the DTGs written by single laser pulses at 193 nm in a low-germanium doped silica fiber, and the therm...
We experimentally demonstrate the ability to simultaneously tune the spectral and polarization properties of biphotons through cascading two biphoton sources and altering the dispersion and birefringence properties of the medium in between.
We demonstrate ultrasound detection with 500-μm-diameter photonic-crystal slab (PCS) sensors fabricated from CMOS-compatible technology. An ultrasound signal impinging a PCS sensor causes a local modulation of the refractive index (RI) of the medium (water) in which the PCS is immersed, resulting in a periodic spectral shift of the optical resonanc...
Measuring the dispersion of photonic devices with small dispersion-length products is challenging due to the phase-sensitive and alignment-intensive nature of conventional methods. In this Letter, we demonstrate a quantum technique to extract the second- and third-order chromatic dispersion of a short single-mode fiber using a fiber-based quantum n...
The twin-field (TF) quantum key distribution (QKD) protocol and its variants are highly attractive because they can beat the well-known rate-loss limit (i.e., the PLOB bound) for QKD protocols without quantum repeaters. In this paper, we perform a proof-of-principle experimental demonstration of TF-QKD based on the protocol proposed by Curty et al....
Multiplexing fiber-optic sensors is an effective way to perform large-area quasi-distributed sensing. Among many sensor multiplexing and interrogation methods, frequency-shifted interferometry (FSI) emerges as a unique, low-cost technique that is capable of resolving sensor locations using a continuous-wave broadband source, a bidirectional optical...
We present a proof-of-principle experimental demonstration of a reconfigurable entanglement distribution scheme utilizing a poled fiber-based source of broadband polarization-entangled photon pairs and dense wavelength-division multiplexing. A large bandwidth ( > 90 nm , centered at 1555 nm) and highly spectrally correlated nature of the entangled...
A CMOS-compatible photonic crystal slab (PCS) sensor is used to detect ultrasound signals in water. The range of detection spans 160 kPa down to a noise-equivalent pressure (NEP) of 650 Pa (3.7 Pa/ Hz). The detection bandwidth spans 1 to 38 MHz, limited only by our measurement apparatus.
In this article, we report a compact, low-power laser diode-pumped, all-fiber polarization-entangled photon pair source based on periodically-poled silica fiber technology. The all-fiber source offers room-temperature alignment-free turn-key operation with low power consumption, and is packaged into a fanless, portable enclosure. It features a broa...
We demonstrate the detection of ultrasound signals with 500-micron-diameter photonic-crystal slab (PCS) sensors fabricated from CMOS-compatible technology. An ultrasound signal impinging a PCS sensor causes a local modulation of the refractive index (RI) of the medium (water) in which the PCS is immersed, resulting in a periodic spectral shift of t...
In this letter, we report a compact, low-power laser diode-pumped, all-fiber polarization-entangled photon pair source based on periodically-poled silica fiber technology. The all-fiber source offers room-temperature, alignment-free, turn-key operation, with low power consumption, and is packaged into a fanless, portable enclosure. It features a br...
In classical optics, interference occurs between two optical fields when they are indistinguishable from one another. The same holds true in quantum optics, where a particular experiment, the Franson interferometer, involves the interference of a photon pair with a time-delayed version of itself. The canonical version of this interferometer require...
