Showing papers by "Jeffrey H. Shapiro published in 2017"
TL;DR: In this article, a commercially available dispersion compensation module (DCM) with a dispersion equivalent to 100 km of standard optical fiber and with an insertion loss of only 2.8 dB was used to obtain high spectral resolution in a much shorter measurement time.
Abstract: Spectrally unentangled biphotons with high single-spatiotemporal-mode purity are highly desirable for many quantum information processing tasks. We generate biphotons with an inferred heralded-state spectral purity of 99%, the highest to date without any spectral filtering, by pulsed spontaneous parametric downconversion in a custom-fabricated periodically-poled KTiOPO4 crystal under extended Gaussian phase-matching conditions. To efficiently characterize the joint spectral intensity of the generated biphotons at high spectral resolution, we employ a commercially available dispersion compensation module (DCM) with a dispersion equivalent to 100 km of standard optical fiber and with an insertion loss of only 2.8 dB. Compared with the typical method of using two temperature-stabilized equal-length fibers that incurs an insertion loss of 20 dB per fiber, the DCM approach achieves high spectral resolution in a much shorter measurement time. Because the dispersion amount and center wavelengths of DCMs can be easily customized, spectral characterization in a wide range of quantum photonic applications should benefit significantly from this technique.
74 citations
TL;DR: In this paper, the authors used FF-SFG reception to determine the receiver operating characteristic (detection probability versus false-alarm probability) for optimum QI target detection under the Neyman-Pearson criterion.
Abstract: Quantum illumination (QI) provides entanglement-based target detection—in an entanglement-breaking environment—whose performance is significantly better than that of optimum classical-illumination target detection. QI’s performance advantage was established in a Bayesian setting with the target presumed equally likely to be absent or present and error probability employed as the performance metric. Radar theory, however, eschews that Bayesian approach, preferring the Neyman–Pearson performance criterion to avoid the difficulties of accurately assigning prior probabilities to target absence and presence and appropriate costs to false-alarm and miss errors. We have recently reported an architecture—based on sum-frequency generation (SFG) and feedforward (FF) processing—for minimum error-probability QI target detection with arbitrary prior probabilities for target absence and presence. In this paper, we use our results for FF-SFG reception to determine the receiver operating characteristic—detection probability versus false-alarm probability—for optimum QI target detection under the Neyman–Pearson criterion.
55 citations
TL;DR: Spectrally unentangled biphotons are generated with an inferred heralded-state spectral purity of 99%, the highest to date without any spectral filtering, by pulsed spontaneous parametric downconversion in a custom-fabricated periodically-poled KTiOPO4 crystal under extended Gaussian phase-matching conditions.
Abstract: Spectrally unentangled biphotons with high single-spatiotemporal-mode purity are highly desirable for many quantum information processing tasks. We generate biphotons with an inferred heralded-state spectral purity of 99%, the highest to date without any spectral filtering, by pulsed spontaneous parametric downconversion in a custom-fabricated periodically-poled KTiOPO$_4$ crystal under extended Gaussian phase-matching conditions. To efficiently characterize the joint spectral intensity of the generated biphotons at high spectral resolution, we employ a commercially available dispersion compensation module (DCM) with a dispersion equivalent to 100 km of standard optical fiber and with an insertion loss of only 2.8 dB. Compared with the typical method of using two temperature-stabilized equal-length fibers that incurs an insertion loss of 20 dB per fiber, the DCM approach achieves high spectral resolution in a much shorter measurement time. Because the dispersion amount and center wavelengths of DCMs can be easily customized, spectral characterization in a wide range of quantum photonic applications should benefit significantly from this technique.
46 citations
TL;DR: Zhuang et al. as discussed by the authors show that the sum-frequency generation receiver achieves QI's full 6 dB advantage over optimum classical operation for Rayleigh-fading targets, but this performance is subexponential: its error probability is lower than the classical system's.
Abstract: Quantum illumination (QI) is an entanglement-enhanced sensing system whose performance advantage over a comparable classical system survives its usage in an entanglement-breaking scenario plagued by loss and noise. In particular, QI's error-probability exponent for discriminating between equally likely hypotheses of target absence or presence is 6 dB higher than that of the optimum classical system using the same transmitted power. This performance advantage, however, presumes that the target return, when present, has known amplitude and phase, a situation that seldom occurs in light detection and ranging (lidar) applications. At lidar wavelengths, most target surfaces are sufficiently rough that their returns are speckled, i.e., they have Rayleigh-distributed amplitudes and uniformly distributed phases. QI's optical parametric amplifier receiver---which affords a 3 dB better-than-classical error-probability exponent for a return with known amplitude and phase---fails to offer any performance gain for Rayleigh-fading targets. We show that the sum-frequency generation receiver [Zhuang et al., Phys. Rev. Lett. 118, 040801 (2017)]---whose error-probability exponent for a nonfading target achieves QI's full 6 dB advantage over optimum classical operation---outperforms the classical system for Rayleigh-fading targets. In this case, QI's advantage is subexponential: its error probability is lower than the classical system's by a factor of $1/ln(M\overline{\ensuremath{\kappa}}{N}_{S}/{N}_{B})$, when $M\overline{\ensuremath{\kappa}}{N}_{S}/{N}_{B}\ensuremath{\gg}1$, with $M\ensuremath{\gg}1$ being the QI transmitter's time-bandwidth product, ${N}_{S}\ensuremath{\ll}1$ its brightness, $\overline{\ensuremath{\kappa}}$ the target return's average intensity, and ${N}_{B}$ the background light's brightness.
45 citations
TL;DR: A proof-of-concept experiment included 10 dB propagation loss and achieved a 55 Mbit/s secret-key rate (SKR) for a 100 M bit/s modulation rate, representing ~500-fold and ~50-fold improvements in secret- key efficiency (SKE) and SKR (bits per second), respectively.
Abstract: Floodlight quantum key distribution (FL-QKD) is a radically different QKD paradigm that can achieve gigabit-per-second secret-key rates over metropolitan area distances without multiplexing [Q. Zhuang et al., Phys. Rev. A 94, 012322 (2016)]. It is a two-way protocol that transmits many photons per bit duration and employs a high-gain optical amplifier, neither of which can be utilized by existing QKD protocols, to mitigate channel loss. FL-QKD uses an optical bandwidth that is substantially larger than the modulation rate and performs decoding with a unique broadband homodyne receiver. Essential to FL-QKD is Alice's injection of photons from a photon-pair source---in addition to the light used for key generation---into the light she sends to Bob. This injection enables Alice and Bob to quantify Eve's intrusion and thus secure FL-QKD against collective attacks. Our proof-of-concept experiment included 10 dB propagation loss---equivalent to 50 km of low-loss fiber---and achieved a 55 Mbit/s secret-key rate (SKR) for a 100 Mbit/s modulation rate, as compared to the state-of-the-art system's 1 Mbit/s SKR for a 1 Gbit/s modulation rate [M. Lucamarini et al., Opt. Express 21, 24550 (2013)], representing $\ensuremath{\sim}500$-fold and $\ensuremath{\sim}50$-fold improvements in secret-key efficiency (bits per channel use) and SKR (bits per second), respectively.
27 citations
Journal Article•
11 citations
24 Aug 2017
TL;DR: This work proposes a constrained optimization-based frame- work to address extremes in scarcity of photons and blurring by a forward imaging kernel and provides two algorithms for the resulting inverse problem: a greedy algorithm, inspired by sparse pursuit algorithms; and a convex optimization heuristic that incorporates image total variation regularization.
Abstract: The resolution achieved in photon-efficient active optical range imaging systems can be low due to non-idealities such as propagation through a diffuse scattering medium. We propose a constrained optimization-based frame- work to address extremes in scarcity of photons and blurring by a forward imaging kernel. We provide two algorithms for the resulting inverse problem: a greedy algorithm, inspired by sparse pursuit algorithms; and a convex optimization heuristic that incorporates image total variation regularization. We demonstrate that our framework outperforms existing deconvolution imaging techniques in terms of peak signal-to-noise ratio. Since our proposed method is able to super-resolve depth features using small numbers of photon counts, it can be useful for observing fine-scale phenomena in remote sensing through a scattering medium and through-the-skin biomedical imaging applications.
7 citations
TL;DR: An optical scheme, employing optical parametric down-converters interlaced with nonlinear sign gates (NSGs), that completely converts an n-photon Fock-state pump to n signal-idler photon pairs when the down- Converters' crystal lengths are chosen appropriately is proposed.
Abstract: We propose an optical scheme, employing optical parametric down-converters interlaced with nonlinear sign gates (NSGs), that completely converts an n-photon Fock-state pump to n signal-idler photon pairs when the down-converters’ crystal lengths are chosen appropriately. The proof of this assertion relies on amplitude amplification, analogous to that employed in Grover search, applied to the full quantum dynamics of single-mode parametric down-conversion. When we require that all Grover iterations use the same crystal, and account for potential experimental limitations on crystal-length precision, our optimized conversion efficiencies reach unity for 1 ≤ n ≤ 5, after which they decrease monotonically for n values up to 50, which is the upper limit of our numerical dynamics evaluations. Nevertheless, our conversion efficiencies remain higher than those for a conventional (no NSGs) down-converter.
6 citations
14 May 2017
TL;DR: In this article, the authors review theory and experiments for quantum illumination-entanglement-based protocols for enhanced target detection and secure classical communication and show that floodlight quantum key distribution, affords Gbps secret-key rates over metropolitan-area distances.
Abstract: We review theory and experiments for quantum illumination-entanglement-based protocols for enhanced target detection and secure classical communication-and show that its unentangled descendant, floodlight quantum key distribution, affords Gbps secret-key rates over metropolitan-area distances.
3 citations
TL;DR: In this article, a coherent state Mach-Zehnder interferometer (MZI) with parity-based phase estimation was shown to achieve SNL scaling in a single measurement, albeit without superresolution.
Abstract: Previous studies [J. Opt. Soc. Am. B27, A170 (2010)JOBPDE0740-322410.1364/JOSAB.27.00A170; J. Appl. Phys.114, 193102 (2013)JAPIAU0021-897910.1063/1.4829016] have asserted that a coherent-state Mach–Zehnder interferometer (MZI) with parity-based phase estimation can achieve superresolution at the shot-noise limit (SNL). We show that these studies have ignored the need for repeated measurements in order to achieve root-mean-square accuracy at the SNL. Consequently, their superresolution claims need major revision. For comparison, we present the performance of a coherent-state MZI that uses dual-homodyne detection and show that it can achieve SNL scaling in a single measurement, albeit without superresolution.
3 citations
Posted Content•
TL;DR: In this paper, the authors reported an FL-QKD experiment operating at a 1.3 Gbit/s secret key rate over a 10dB-loss channel, which is the first QKD demonstration that achieves a gigabit-per-second-class SKR.
Abstract: Quantum key distribution (QKD) enables unconditionally secure communication ensured by the laws of physics, opening a promising route to security infrastructure for the coming age of quantum computers. QKD's demonstrated secret-key rates (SKRs), however, fall far short of the gigabit-per-second rates of classical communication, hindering QKD's widespread deployment. QKD's low SKRs are largely due to existing single-photon-based protocols' vulnerability to channel loss. Floodlight QKD (FL-QKD) boosts SKR by transmitting many photons per encoding, while offering security against collective attacks. Here, we report an FL-QKD experiment operating at a 1.3 Gbit/s SKR over a 10-dB-loss channel. To the best of our knowledge, this is the first QKD demonstration that achieves a gigabit-per-second-class SKR, representing a critical advance toward high-rate QKD at metropolitan-area distances.
Posted Content•
11 Apr 2017
TL;DR: In this paper, it was shown that universal quantum computation can be realized using only linear optics and three-wave mixing interactions in any $(n+1)$-dimensional qudit basis of the $n$-pump-photon subspace.
Abstract: We prove that universal quantum computation can be realized---using only linear optics and $\chi^{(2)}$ (three-wave mixing) interactions---in any $(n+1)$-dimensional qudit basis of the $n$-pump-photon subspace. First, we exhibit a strictly universal gate set for the qubit basis in the one-pump-photon subspace. Next, we demonstrate qutrit-basis universality by proving that $\chi^{(2)}$ Hamiltonians and photon-number operators generate the full $\mathfrak{u}(3)$ Lie algebra in the two-pump-photon subspace, and showing how the qutrit controlled-$Z$ gate can be implemented with only linear optics and $\chi^{(2)}$ interactions. We then use proof by induction to obtain our general qudit result. Our induction proof relies on coherent photon injection/subtraction, a technique enabled by $\chi^{(2)}$ interaction between the encoding modes and ancillary modes. Finally, we show that coherent photon injection is more than a conceptual tool in that it offers a route to preparing high-photon-number Fock states from single-photon Fock states.
14 May 2017
TL;DR: It is shown that FL-QKD's SKR can be doubled by using 32-ary PSK, and this work has shown that binary phase-shift keying of multiple optical modes can achieve Gbps secret-key rates at metropolitan-area distances.
Abstract: Floodlight quantum key distribution (FL-QKD) uses binary phase-shift keying (BPSK) of multiple optical modes to achieve Gbps secret-key rates (SKRs) at metropolitan-area distances. We show that FL-QKD's SKR can be doubled by using 32-ary PSK.
14 May 2017
TL;DR: In this paper, the authors generate biphotons via pulsed spontaneous parametric downconversion under extended Gaussian phase matching, and measure their joint spectral intensity at high resolution using a low-loss dispersion compensation module to obtain a 99% heralded state spectral purity.
Abstract: We generate biphotons via pulsed spontaneous parametric downconversion under extended Gaussian phase matching, and measure their joint spectral intensity at high resolution using a low-loss dispersion compensation module to obtain a 99% heralded-state spectral purity.
Journal Article•
TL;DR: Zhuang et al. as discussed by the authors show that the sum-frequency generation receiver achieves QI's full 6 dB advantage over optimum classical operation for Rayleigh-fading targets, but this performance is subexponential: its error probability is lower than the classical system's.
Abstract: Quantum illumination (QI) is an entanglement-enhanced sensing system whose performance advantage over a comparable classical system survives its usage in an entanglement-breaking scenario plagued by loss and noise. In particular, QI's error-probability exponent for discriminating between equally likely hypotheses of target absence or presence is 6 dB higher than that of the optimum classical system using the same transmitted power. This performance advantage, however, presumes that the target return, when present, has known amplitude and phase, a situation that seldom occurs in light detection and ranging (lidar) applications. At lidar wavelengths, most target surfaces are sufficiently rough that their returns are speckled, i.e., they have Rayleigh-distributed amplitudes and uniformly distributed phases. QI's optical parametric amplifier receiver---which affords a 3 dB better-than-classical error-probability exponent for a return with known amplitude and phase---fails to offer any performance gain for Rayleigh-fading targets. We show that the sum-frequency generation receiver [Zhuang et al., Phys. Rev. Lett. 118, 040801 (2017)]---whose error-probability exponent for a nonfading target achieves QI's full 6 dB advantage over optimum classical operation---outperforms the classical system for Rayleigh-fading targets. In this case, QI's advantage is subexponential: its error probability is lower than the classical system's by a factor of $1/ln(M\overline{\ensuremath{\kappa}}{N}_{S}/{N}_{B})$, when $M\overline{\ensuremath{\kappa}}{N}_{S}/{N}_{B}\ensuremath{\gg}1$, with $M\ensuremath{\gg}1$ being the QI transmitter's time-bandwidth product, ${N}_{S}\ensuremath{\ll}1$ its brightness, $\overline{\ensuremath{\kappa}}$ the target return's average intensity, and ${N}_{B}$ the background light's brightness.