Daniel Soh

Interests

Research

Quantum network, quantum optics, quantum sensing, connected quantum systems, quantum machine learning, reservoir computing, quantum deep neural network

Teaching

Initializing the fundamentals for learning quantum information science in the future; deeply diving into the structures of quantum mechanics theory; studying the fundamentals of machine learning

Courses

Scholarly Contributions

Books

• Soh, D. (2019). 2D materials and nonlinear quantum optics. Stanford University.

Journals/Publications

• Brif, C., Sarovar, M., Soh, D. B., Farley, D. R., & Bisson, S. E. (2024). Optimizing squeezing in a coherent quantum feedback network of optical parametric oscillators.
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  Advances in the emerging field of coherent quantum feedback control (CQFC)have led to the development of new capabilities in the areas of quantum controland quantum engineering, with a particular impact on the theory andapplications of quantum optical networks. We consider a CQFC network consistingof two coupled optical parametric oscillators (OPOs) and study the squeezingspectrum of its output field. The performance of this network as asqueezed-light source with desired spectral characteristics is optimized bysearching over the space of model parameters with experimentally motivatedbounds. We use the QNET package to model the network's dynamics and the PyGMOpackage of global optimization algorithms to maximize the degree of squeezingat a selected sideband frequency or the average degree of squeezing over aselected bandwidth. The use of global search methods is critical foridentifying the best possible performance of the CQFC network, especially forsqueezing at higher-frequency sidebands and higher bandwidths. The resultsdemonstrate that the CQFC network of two coupled OPOs makes it possible to varythe squeezing spectrum, effectively utilize the available pump power, andoverall significantly outperform a single OPO. Additionally, the Hessianeigenvalue analysis shows that the squeezing generation performance of theoptimally operated CQFC network is robust to small variations of phaseparameters.[Journal_ref: ]
• Chatterjee, E., Soh, D., & Eichenfield, M. (2024). Ab-Initio Calculations of Nonlinear Susceptibility and Multi-Phonon Mixing Processes in a 2D Electron Gas Coupled to a Piezoelectric Material. Bulletin of the American Physical Society.
• Chatterjee, E., Wendt, A., Soh, D., & Eichenfield, M. (2024). Ab initio calculations of nonlinear susceptibility and multiphonon mixing processes in a 2DEG-piezoelectric heterostructure. Physical Review Research, 6(2), 023288.
• Chatterjee, E., Wendt, A., Soh, D., & Eichenfield, M. (2024). Ab-Initio Calculations of Nonlinear Susceptibility and Multi-Phonon Mixing Processes in a 2DEG-Piezoelectric Heterostructure.
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  Solid-state elastic-wave phonons are a promising platform for a wide range ofquantum information applications. An outstanding challenge and enablingcapability in harnessing phonons for quantum information processing isachieving strong nonlinear interactions between them. To this end, we propose ageneral architecture using piezoelectric-semiconductor heterostructuresconsisting of a piezoelectric acoustic material hosting phonon modes in directproximity to a two-dimensional electron gas (2DEG). Each phonon in thepiezoelectric material carries an electric field, which extends into the 2DEG.The fields induce polarization of 2DEG electrons, which in turn interact withother piezoelectric phononic electric fields. The net result is couplingbetween the various phonon modes. We derive, from first principles, thenonlinear phononic susceptibility of the system. We show that many nonlinearprocesses are strongly favored at high electron mobility, motivating the use ofthe 2DEG to mediate the nonlinearities. We derive in detail the first, second,and third-order susceptibilities and calculate them for the case of a lithiumniobate surface acoustic wave interacting with a GaAs-AlGaAs heterostructure2DEG. We show that, for this system, the strong third-order nonlinearity couldenable single-phonon Kerr shift in an acoustic cavity that exceeds realisticcavity linewidths, potentially leading to a new class of acoustic qubit. Wefurther show that the strong second-order nonlinearity could be used to producea high-gain, traveling-wave parametric amplifier to amplify--and ultimatelydetect--the outputs of the acoustic cavity qubits. Assuming favorable losses insuch a system, these capabilities, combined with the ability to efficientlytransduce phonons from microwave electromagnetic fields in transmission lines,thus hold promise for creating all-acoustic quantum information processors.[Journal_ref: ]
• Chrostoski, P., Bisson, S., & Soh, D. (2024). Limitations of a large momentum atom interferometer acceleration sensor due to spontaneous emission. Bulletin of the American Physical Society.
• Chrostoski, P., Bisson, S., Farley, D., Narducci, F., & Soh, D. (2024). Error analysis in large area multi-Raman pulse atom interferometry due to undesired spontaneous decay.
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  Despite the fact that atom interferometry has been a successful applicationof quantum sensing, a major topic of interest is the further improvement of thesensitivity of these devices. In particular, the area enclosed by theinterferometer (which controls the sensitivity) can be increased by providing alarger momentum kick to the atom cloud, increasing the extent of the momentumaxis. One such atom optics technique involves increasing the number of central$\pi-$Raman pulses. This technique, while providing the prerequisite additionalmomentum boost, also causes the atom to remain in the intermediate high energystate for longer periods of time. This additional length of time is oftenneglected in many treatments due to the adiabatic elimination of the higherenergy state enabled by the large optical detuning. The increased time in theintermediate high energy state results in a higher probability of undesiredspontaneous decay and a loss of quantum information, thereby adding error tothe atom interferometer. In this work, we consider an open quantum system usingthe Lindblad master equation to devise a model for the atomic state dynamicsthat includes the undesired spontaneous decay from the intermediate high energystate. We formulate an error figure of merit to analyze limitations of an atominterferometer configured for acceleration measurements. Our theoreticalresults show the error figure of merit will be dominated by a $N_{R}^{-2}$scaling factor for low numbers of $\pi-$Raman pulses, but will be dominated bya monotonic increase in error for high number of $\pi-$Raman pulses. Wedetermined the number of $\pi$-Raman pulses that accomplishes maximal momentumtransfer with a the minimal error, depending on major system parameters.[Journal_ref: ]
• Chrostoski, P., Bisson, S., Farley, D., Narducci, F., & Soh, D. (2024). Error analysis in large area multi-Raman pulse atom interferometry due to undesired spontaneous decay. arXiv preprint arXiv:2403.08913.
• Cuozzo, J. J., Yu, W., Davids, P., Nenoff, T. M., Soh, D. B., Pan, W., & Rossi, E. (2024). Leggett modes in a Dirac semimetal. Nature Physics, 1--6.
• Ehlers, P. J., Nurdin, H. I., & Soh, D. (2024). Improving the Performance of Echo State Networks Through Feedback.
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  Reservoir computing, using nonlinear dynamical systems, offers acost-effective alternative to neural networks for complex tasks involvingprocessing of sequential data, time series modeling, and system identification.Echo state networks (ESNs), a type of reservoir computer, mirror neuralnetworks but simplify training. They apply fixed, random linear transformationsto the internal state, followed by nonlinear changes. This process, guided byinput signals and linear regression, adapts the system to match targetcharacteristics, reducing computational demands. A potential drawback of ESNsis that the fixed reservoir may not offer the complexity needed for specificproblems. While directly altering (training) the internal ESN would reintroducethe computational burden, an indirect modification can be achieved byredirecting some output as input. This feedback can influence the internalreservoir state, yielding ESNs with enhanced complexity suitable for broaderchallenges. In this paper, we demonstrate that by feeding some component of thereservoir state back into the network through the input, we can drasticallyimprove upon the performance of a given ESN. We rigorously prove that, for anygiven ESN, feedback will almost always improve the accuracy of the output. Fora set of three tasks, each representing different problem classes, we find thatwith feedback the average error measures are reduced by $30\%-60\%$.Remarkably, feedback provides at least an equivalent performance boost todoubling the initial number of computational nodes, a computationally expensiveand technologically challenging alternative. These results demonstrate thebroad applicability and substantial usefulness of this feedback scheme.[Journal_ref: ]
• Ehlers, P. J., Nurdin, H. I., & Soh, D. (2024). Improving the performance of echo state networks through state feedback. Neural Networks, 107101.
• Ehlers, P. J., Nurdin, H. I., & Soh, D. (2024). Stochastic Reservoir Computers.
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  Reservoir computing is a form of machine learning that utilizes nonlineardynamical systems to perform complex tasks in a cost-effective manner whencompared to typical neural networks. Many recent advancements in reservoircomputing, in particular quantum reservoir computing, make use of reservoirsthat are inherently stochastic. However, the theoretical justification forusing these systems has not yet been well established. In this paper, weinvestigate the universality of stochastic reservoir computers, in which we usea stochastic system for reservoir computing using the probabilities of eachreservoir state as the readout instead of the states themselves. In stochasticreservoir computing, the number of distinct states of the entire reservoircomputer can potentially scale exponentially with the size of the reservoirhardware, offering the advantage of compact device size. We prove that classesof stochastic echo state networks, and therefore the class of all stochasticreservoir computers, are universal approximating classes. We also investigatethe performance of two practical examples of stochastic reservoir computers inclassification and chaotic time series prediction. While shot noise is alimiting factor in the performance of stochastic reservoir computing, we showsignificantly improved performance compared to a deterministic reservoircomputer with similar hardware in cases where the effects of noise are small.[Journal_ref: ]
• Ehlers, P. J., Nurdin, H. I., & Soh, D. (2024). Stochastic Reservoir Computers. arXiv preprint arXiv:2405.12382.
• Pan, W., Soh, D., Yu, W., Davids, P., & Nenoff, T. M. (2021). Microwave response in a topological superconducting quantum interference device. Scientific Reports.
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  Photon detection at microwave frequency is of great interest due to its application in quantum computation information science and technology. Herein are results from studying microwave response in a topological superconducting quantum interference device (SQUID) realized in Dirac semimetal Cd3As2. The temperature dependence and microwave power dependence of the SQUID junction resistance are studied, from which we obtain an effective temperature at each microwave power level. It is observed the effective temperature increases with the microwave power. This observation of microwave response may pave the way for single photon detection at the microwave frequency in topological quantum materials. [Journal_ref: Scientific Reports 11, 8615 (2021)]
• Pizzimenti, A. J., & Soh, D. (2024). Optical Gottesman-Kitaev-Preskill qubit generation via approximate squeezed coherent state superposition breeding. Physical Review A, 110(6), 062619.
• Soh, D., & Young, S. (2024). Fundamental limits to the highly-displaced bright squeezed light generation based on linear optics and parametric processes. Bulletin of the American Physical Society.
• Soh, D., Ehlers, P., & Nurdin, H. (2024). Reservoir Computing with Feedback for Quantum State Identification. Bulletin of the American Physical Society.
• Young, S. M., & Soh, D. (2024). Fundamental limits to the generation of highly displaced bright squeezed light using linear optics and parametric amplifiers.
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  High quality squeezed light is an important resource for a variety ofapplications. Multiple methods for generating squeezed light are known, havingbeen demonstrated theoretically and experimentally. However, the effectivenessof these methods -- in particular, the inherent limitations to the signals thatcan be produced -- has received little consideration. Here we present acomparative theoretical analysis for generating a highly-displacedhigh-brightness squeezed light from a linear optical method -- a beam-splittermixing a squeezed vacuum and a strong coherent state -- and parametricamplification methods including an optical parametric oscillator, an opticalparametric amplifier, and a dissipative optomechanical squeezer seeded withcoherent states. We show that the quality of highly-displaced high-brightnesssqueeze states that can be generated using these methods is limited on afundamental level by the physical mechanism utilized; across all methods thereare significant tradeoffs between brightness, squeezing, and overalluncertainty. We explore the nature and extent of these tradeoffs specific toeach mechanism and identify the optimal operation modes for each, and providean argument for why this type of tradeoff is unavoidable for parametricamplifier type squeezers.[Journal_ref: ]
• Zhu, C., Ehlers, P. J., Nurdin, H. I., & Soh, D. (2024). Minimalistic and Scalable Quantum Reservoir Computing Enhanced with Feedback.
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  Quantum Reservoir Computing (QRC) leverages quantum systems to performcomplex computational tasks with exceptional efficiency and reduced energyconsumption. We introduce a minimalistic QRC framework utilizing only a fewtwo-level atoms in a single-mode optical cavity, combined with continuousquantum measurements. To achieve high computational expressivity with minimalhardware, we include two critical elements: reservoir feedback and polynomialregression. Reservoir feedback modifies the reservoir's dynamics withoutaltering its hardware, while polynomial regression enhances output resolutionby nonlinearly extending expressions. We evaluate QRC's memory retention andnonlinear data processing through two tasks: predicting chaotic time-seriesdata via the Mackey-Glass task and classifying sine-square waveforms. Ourresults demonstrate significant QRC performance with minimal reservoirscontaining as few as five atoms, further enhanced by feedback mechanisms andpolynomial regression. This framework fulfills QRC's objectives to minimizehardware size and energy consumption, marking a significant advancement inintegrating quantum physics with machine learning technology.[Journal_ref: ]
• Zhu, C., Ehlers, P. J., Nurdin, H. I., & Soh, D. (2024). Practical and Scalable Quantum Reservoir Computing. arXiv preprint arXiv:2405.04799.
• Chatterjee, E., Pan, W., & Soh, D. (2023). Ultra-high-precision detection of single microwave photons based on a hybrid system between a Majorana zero mode and a quantum dot. Physical Review Research, 5(1), 013034.
• Soh, D., & Chatterjee, E. (2023). Label-free quantum super-resolution imaging using entangled multi-mode squeezed light. New Journal of Physics, 25(9), 093001. doi:https://doi.org/10.1088/1367-2630/acf2ba
• Chatterjee, E., Soh, D., & Eichenfield, M. (2022). Optimal quantum transfer from input flying qubit to lossy quantum memory. Journal of Physics A: Mathematical and Theoretical, 55(10), 105302.
• Taylor, J. C., Chatterjee, E., Kindel, W. F., Soh, D., & Eichenfield, M. (2022). Reconfigurable quantum phononic circuits via piezo-acoustomechanical interactions. npj Quantum Information, 8(1), 19.
• Chatterjee, E., Pan, W., & Soh, D. (2021). Microwave Photon Number Resolving Detector Using the Topological Surface State of Superconducting Cadmium Arsenide. Phys. Rev. Research.
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  Photon number resolving detectors play a central role in quantum optics. A key challenge in resolving the number of absorbed photons in the microwave frequency range is finding a suitable material that provides not only an appropriate band structure for absorbing low-energy photons but also a means of detecting a discrete photoelectron excitation. To this end, we propose to measure the temperature gain after absorbing a photon using superconducting cadmium arsenide (Cd3As2) with a topological semimetallic surface state as the detector. The surface electrons absorb the incoming photons and then transfer the excess energy via heat to the superconducting bulk's phonon modes. The temperature gain can be determined by measuring the change in the zero-bias bulk resistivity, which does not significantly affect the lattice dynamics. Moreover, the obtained temperature gain scales discretely with the number of absorbed photons, enabling a photon-number resolving function. Here, we will calculate the temperature increase as a function of the number and frequency of photons absorbed. We will also derive the timescale for the heat transfer process from the surface electrons to the bulk phonons. We will specifically show that the transfer processes are fast enough to ignore heat dissipation loss. [Journal_ref: Phys. Rev. Research 3, 023046 (2021)]
• Pan, W., Soh, D., Yu, W., Davids, P., & Nenoff, T. M. (2021). Microwave response in a topological superconducting quantum interference device. Scientific reports, 11(1), 8615.
  More info

  Photon detection at microwave frequency is of great interest due to its application in quantum computation information science and technology. Herein are results from studying microwave response in a topological superconducting quantum interference device (SQUID) realized in Dirac semimetal CdAs. The temperature dependence and microwave power dependence of the SQUID junction resistance are studied, from which we obtain an effective temperature at each microwave power level. It is observed the effective temperature increases with the microwave power. This observation of large microwave response may pave the way for single photon detection at the microwave frequency in topological quantum materials.
• Soh, D., Chatterjee, E., & Eichenfield, M. (2021). High-fidelity State Transfer Between Leaky Quantum Memories. Phys. Rev. Research.
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  We derive the optimal analytical quantum-state-transfer control solutions for two disparate quantum memory blocks. Employing the SLH formalism description of quantum network theory, we calculate the full quantum dynamics of system populations, which lead to the optimal solution for the highest quantum fidelity attainable. We show that, for the example where the mechanical modes of two optomechanical oscillators act as the quantum memory blocks, their optical modes and a waveguide channel connecting them can be used to achieve a quantum state transfer fidelity of 96% with realistic parameters using our derived optimal control solution. The effects of the intrinsic losses and the asymmetries in the physical memory parameters are discussed quantitatively. [Journal_ref: Phys. Rev. Research 3, 033027 (2021)]
• Chatterjee, E., Soh, D. B., Rogers, C., Gray, D. J., & Mabuchi, H. (2019). Low-Temperature Annihilation Rate for Quasi-Localized Excitons in Monolayer MoS2. Phys. Rev. B.
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  The strong Coulomb forces in monolayer transition metal dichalcogenides ensure that optical excitation of band electrons gives rise to Wannier-Mott excitonic states, each of which can be conceptualized as a composite of a Gaussian wavepacket corresponding to center-of-mass motion and an orbital state corresponding to the motion of the electron and hole about the center-of-mass. Here, we show that at low temperature in monolayer MoS2, given quasi-localized excitons and consequently a significant inter-exciton spacing, the excitons undergo dipole-dipole interaction and annihilate one another in a manner analogous to Auger recombination. To construct our model, we assume that each exciton is localized in a region whose length is on the same scale as the excitonic diameter, thus causing the exciton to behave in a fermionic manner, while the distance between neighboring excitons is much larger than the exciton diameter. We construct the orbital ladder operators for each exciton and apply Fermi's Golden Rule to derive the overall recombination rate as a function of exciton density. [Journal_ref: Phys. Rev. B 100, 155405 (2019)]
• Soh, D. B., Yanagimoto, R., Chatterjee, E., & Mabuchi, H. (2019). Nonlinear optical response of a local surface plasmon coupled to a 2D material. arXiv.
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  We present a theoretical study of the optical response of a nonlinear oscillator formed by coupling a metal nanoparticle local surface plasmon resonance to excitonic degrees of freedom in a monolayer transition-metal dichalcogenide. We show that the combined system should exhibit strong anharmonicity in its low-lying states, predicting for example a seven order-of-magnitude increase in nonlinearity relative to a silicon photonic crystal cavity. Then, we demonstrate that such system exhibits strong quantum features such as antibunching and non-Gaussianity. Arrays of such nanoscale nonlinear oscillators could be used to realize novel optical metamaterials; alternatively, an individual nanoparticle-monolayer construct could be coupled to an optical resonator to mediate efficient input-output coupling to propagating fields. [Journal_ref: ]
• Soh, D. B., Rogers, C., Gray, D. J., Chatterjee, E., & Mabuchi, H. (2018). Optical nonlinearities of excitons in monolayer MoS2. Phys. Rev. B.
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  We calculate linear and nonlinear optical susceptibilities arising from the excitonic states of mono- layer MoS2 for in-plane light polarizations, using second-quantized bound and unbound exciton operators. Optical selection rules are critical for obtaining the susceptibilities. We derive the valley-chirality rule for the second harmonic generation in monolayer MoS2, and find that the third- harmonic process is efficient only for linearly polarized input light while the third-order two photon process (optical Kerr effect) is efficient for circularly polarized light using a higher order exciton state. The absence of linear absorption due to the band gap and the unusually strong two-photon third-order nonlinearity make the monolayer MoS2 excitonic structure a promising resource for coherent nonlinear photonics. [Journal_ref: Phys. Rev. B 97, 165111 (2018)]
• Sarovar, M., Soh, D. B., Cox, J., Brif, C., DeRose, C. T., Camacho, R., & Davids, P. (2016). Silicon nanophotonics for scalable quantum coherent feedback networks. EPJ Quantum Technology,.
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  The emergence of coherent quantum feedback control (CQFC) as a new paradigm for precise manipulation of dynamics of complex quantum systems has led to the development of efficient theoretical modeling and simulation tools and opened avenues for new practical implementations. This work explores the applicability of the integrated silicon photonics platform for implementing scalable CQFC networks. If proven successful, on-chip implementations of these networks would provide scalable and efficient nanophotonic components for autonomous quantum information processing devices and ultra-low-power optical processing systems at telecommunications wavelengths. We analyze the strengths of the silicon photonics platform for CQFC applications and identify the key challenges to both the theoretical formalism and experimental implementations. In particular, we determine specific extensions to the theoretical CQFC framework (which was originally developed with bulk-optics implementations in mind), required to make it fully applicable to modeling of linear and nonlinear integrated optics networks. We also report the results of a preliminary experiment that studied the performance of an in situ controllable silicon nanophotonic network of two coupled cavities and analyze the properties of this device using the CQFC formalism. [Journal_ref: EPJ Quantum Technology, 3, 14 (2016)]
• Soh, D. B., Hamerly, R., & Mabuchi, H. (2016). Comprehensive analysis of the optical Kerr coefficient of graphene. Phys. Rev. A.
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  We present a comprehensive analysis of the the nonlinear optical Kerr effect in graphene. We directly solve the S-matrix element to calculate the absorption rate, utilizing the Volkov-Keldysh- type crystal wave functions. We then convert to the nonlinear refractive index coefficients through the Kramers-Kronig relation. In this formalism, the source of Kerr nonlinearity is the interplay of optical fields that cooperatively drive the transition from valence to conduction band. This formalism makes it possible to identify and compute the rates of distinct nonlinear processes that contribute to the Kerr nonlinear refractive index coefficient. The four identified mechanisms are two photon absorption, Raman transition, self coupling, and quadratic AC Stark effect. We also present a comparison of our theory with recent experimental and theoretical results. [Journal_ref: Phys. Rev. A 94, 023845 (2016)]
• Soh, D. B., Brif, C., Coles, P. J., L"utkenhaus, N., Camacho, R. M., Urayama, J., & Sarovar, M. (2015). Self-referenced continuous-variable quantum key distribution protocol. Physical Review X, 5(4), 041010.
• Soh, D. B., Brif, C., Coles, P. J., Lütkenhaus, N., Camacho, R. M., Urayama, J., & Sarovar, M. (2015). Self-referenced continuous-variable quantum key distribution protocol. Phys. Rev. X.
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  We introduce a new continuous-variable quantum key distribution (CV-QKD) protocol, self-referenced CV-QKD, that eliminates the need for transmission of a high-power local oscillator between the communicating parties. In this protocol, each signal pulse is accompanied by a reference pulse (or a pair of twin reference pulses), used to align Alice's and Bob's measurement bases. The method of phase estimation and compensation based on the reference pulse measurement can be viewed as a quantum analog of intradyne detection used in classical coherent communication, which extracts the phase information from the modulated signal. We present a proof-of-principle, fiber-based experimental demonstration of the protocol and quantify the expected secret key rates by expressing them in terms of experimental parameters. Our analysis of the secret key rate fully takes into account the inherent uncertainty associated with the quantum nature of the reference pulse(s) and quantifies the limit at which the theoretical key rate approaches that of the respective conventional protocol that requires local oscillator transmission. The self-referenced protocol greatly simplifies the hardware required for CV-QKD, especially for potential integrated photonics implementations of transmitters and receivers, with minimum sacrifice of performance. As such, it provides a pathway towards scalable integrated CV-QKD transceivers, a vital step towards large-scale QKD networks. [Journal_ref: Phys. Rev. X 5, 041010 (2015)]
• Crisafulli, O., Tezak, N., Soh, D. B., Armen, M. A., & Mabuchi, H. (2013). Squeezed light in an optical parametric oscillator network with coherent feedback quantum control. Optics Express, 21(15), 18371--18386.
• Crisafulli, O., Tezak, N., Soh, D. B., Armen, M. A., & Mabuchi, H. (2013). Squeezed light in an optical parametric oscillator network with coherent feedback quantum control. Optics Express.
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  We present squeezing and anti-squeezing spectra of the output from a degenerate optical parametric oscillator (OPO) network arranged in different coherent quantum feedback configurations. One OPO serves as a quantum plant, the other as a quantum controller. The addition of coherent feedback enables shaping of the output squeezing spectrum of the plant, and is found to be capable of pushing the frequency of maximum squeezing away from the optical driving frequency and broadening the spectrum over a wider frequency band. The experimental results are in excellent agreement with the developed theory, and illustrate the use of coherent quantum feedback to engineer the quantum-optical properties of the plant OPO output. [Journal_ref: ]
• Moore, S. W., Soh, D. B., Bisson, S. E., Patterson, B. D., & Hsu, W. L. (2012). 400 µJ 79 ns amplified pulses from a Q-switched fiber laser using an Yb(3+)-doped fiber saturable absorber. Optics express, 20(21), 23778-89.
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  We report a passively Q-switched all-fiber laser using a large mode area (LMA) Yb(3+)-doped fiber cladding-pumped at 915 nm and an unpumped single-mode Yb(3+)-doped fiber as the saturable absorber (SA). The saturable absorber fiber and gain fiber were coupled with a free-space telescope to optimize the coupling efficiency between the disparate fibers, preferentially bleaching the SA fiber before gain depletion in the pumped fiber. Using this scheme we first demonstrate a Q-switched oscillator with 40 μJ 79 ns pulses at 1026 nm, and show that pulses can be generated from 1020 nm to 1040 nm. The associated peak power of the oscillator alone is more than two orders of magnitude larger than that reported in previous experimental studies using an Yb(3+)-doped fiber as a saturable absorber. We further demonstrate an amplified pulse energy of 0.4 mJ using an Yb(3+)-doped cladding pumped fiber amplifier. Experimental studies in which the saturable absorber length, pump times, and wavelengths are independently varied reveal the impact of these parameters on laser performance.
• Soh, D. B., & Koplow, J. P. (2011). Analysis of spectral broadening of incoherent light in optical fibers with nonzero dispersion. Optical Engineering, 50(11), 111602--111602.
• Soh, D. B., Bisson, S. E., Patterson, B. D., & Moore, S. W. (2011). High-power all-fiber passively Q-switched laser using a doped fiber as a saturable absorber: numerical simulations. Optics letters, 36(13), 2536--2538.
• Soh, D. B., Koplow, J. P., Moore, S. W., Schroder, K. L., & Hsu, W. L. (2010). The effect of dispersion on spectral broadening of incoherent continuous-wave light in optical fibers. Optics express, 18(21), 22393-405.
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  In addition to fiber nonlinearity, fiber dispersion plays a significant role in spectral broadening of incoherent continuous-wave light. In this paper we have performed a numerical analysis of spectral broadening of incoherent light based on a fully stochastic model. Under a wide range of operating conditions, these numerical simulations exhibit striking features such as damped oscillatory spectral broadening (during the initial stages of propagation), and eventual convergence to a stationary, steady state spectral distribution at sufficiently long propagation distances. In this study we analyze the important role of fiber dispersion in such phenomena. We also demonstrate an analytical rate equation expression for spectral broadening.
• Kim, J., Soh, D. B., Nilsson, J., Richardson, D. J., & Sahu, J. K. (2007). Fiber design for high-power low-cost Yb: Al-doped fiber laser operating at 980 nm. IEEE Journal of Selected Topics In Quantum Electronics, 13(3), 588--597.
• Kim, J., Dupriez, P., Soh, D., Nilsson, J., & Sahu, J. K. (2006). Core area scaling of Nd: Al-doped silica depressed clad hollow optical fiber and Q-switched laser operation at 0.9 $mu$m. Optics letters, 31(19), 2833--2835.
• Oh, K., Yoo, S., Ryu, U., Kim, S., Paek, U., Soh, D. B., Sahu, J. K., & Nilsson, J. (2006). Spectral control of optical gain in a rare earth-doped optical fiber using novel triple layered structures. Optical Fiber Technology, 12(4), 297--304.
• Soh, D. B., Nilsson, J., & Grudinin, A. B. (2006). Efficient femtosecond pulse generation using a parabolic amplifier combined with a pulse compressor. I. Stimulated Raman-scattering effects. JOSA B, 23(1), 1--9.
• Jeong, Y., Sahu, J. K., Soh, D., Codemard, C. A., & Nilsson, J. (2005). High-power tunable single-frequency single-mode erbium: ytterbium codoped large-core fiber master-oscillator power amplifier source. Optics letters, 30(22), 2997--2999.
• Soh, D. B., Nilsson, J., Baek, S., Codemard, C., Jeong, Y., & Philippov, V. (2004). Modal power decomposition of beam intensity profiles into linearly polarized modes of multimode optical fibers. Journal of the Optical Society of America. A, Optics, image science, and vision, 21(7), 1241-50.
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  We calculate the modal power distribution of a randomly and linearly polarized (LP) multimode beam inside a cylindrical fiber core from knowledge of spatial-intensity profiles of a beam emitted from the fiber. We provide an exact analysis with rigorous proofs that forms the basis for our calculations. The beam from the fiber end is collimated by a spherical lens with a specific focal length. The original LP-mode basis is transformed by the spherical lens and forms another orthogonal basis that describes the free-space beam. By using this basis, we calculate the modal power distribution from the mutual-intensity profile. This is acquired by adopting a well-known mutual-intensity-profile-retrieving technique based on measurements of the intensity patterns several times after two orthogonal cylindrical lenses with varying separation. The feasibility of our decomposition algorithm is demonstrated with simulations.

Proceedings Publications

• Chatterjee, E., Soh, D., & Eichenfield, M. (2023). Building a Quantum Repeater Using Optomechanical Oscillators as On-Demand Entanglement Sources. In APS March Meeting Abstracts, 2023.
• Chrostoski, P., Bisson, S., & Soh, D. (2023). Limitations of a multi-Raman-pulse atom interferometry acceleration sensor. In APS March Meeting Abstracts, 2023.
• Cuozzo, S. L., Bisson, S., Bartolick, J., Steinmetz, S., Kliewer, C., Chandler, D., & Soh, D. (2023). Quantum-Enhanced Two-Photon Spectroscopy using Squeezed Light. In Frontiers in Optics.
• Chatterjee, E., Pan, W., & Soh, D. (2022). An RF Photon-Number-Resolving Detector Using Majorana Zero Mode. In APS March Meeting Abstracts, 2022.
• Chatterjee, E., Soh, D., & Eichenfield, M. (2022). High-Fidelity Qubit Transfer Between Leaky Memory Blocks. In APS March Meeting Abstracts, 2022.
• Chatterjee, E., Soh, D., & Eichenfield, M. (2022). Optimal Quantum Transfer from Input Flying Qubit to Lossy Memory. In APS March Meeting Abstracts, 2022.
• Chatterjee, E., Soh, D., Lewis, R., Kindel, W., Hackett, L., Taylor, J., & Eichenfield, M. (2022). Long-Distance End-to-End Quantum State Transfer in a Transmon Qubit Network Connected Via Optical Photons. In APS March Meeting Abstracts, 2022.
• Soh, D. (2022). Super-resolution Quantum Imaging using Massively Entangled Multimode Squeezed Light. In APS March Meeting Abstracts, 2022.
• Soh, D., & Eichenfield, M. (2022). Bright Squeezed Light from Dissipative Optomechanical Light Squeezer. In APS March Meeting Abstracts, 2022.
• Soh, D., Chatterjee, E., Rogers, C., Gray, D., & Mabuchi, H. (2019). Optical Selection Rules and Optical Nonlinearities of Excitonic States in Monolayer MoS 2. In APS March Meeting Abstracts, 2019.
• Moore, S. W., Patterson, B. D., Soh, D. B., & Bisson, S. E. (2014). An all-fiber high-energy cladding-pumped 93 nanosecond Q-switched fiber laser using an Y3+-doped fiber saturable absorber. In Fiber Lasers XI: Technology, Systems, and Applications, 8961.
• Soh, D., Patterson, B. D., Bisson, S. E., & Moore, S. W. (2014). An all-fiber high-energy cladding-pumped 93 nanosecond Q-switched fiber laser using an Yb3% 2B-doped fiber saturable absorber.. In Technical Digest of SPIE Photonics West conference.
• Moore, S. W., Soh, D. B., Bisson, S. E., Patterson, B. D., & Hsu, W. L. (2013). A high-energy cladding-pumped 80 nanosecond Q-switched fiber laser using a tapered fiber saturable absorber. In Fiber Lasers X: Technology, Systems, and Applications, 8601.
• Moore, S. W., Soh, D. B., Bisson, S. E., Patterson, B. D., & Hsu, W. L. (2013). Cladding pumped Q-switched fiber laser using a tapered fiber saturable absorber. In CLEO: Science and Innovations.
• Koplow, J. P., & Soh, D. B. (2011). The 4FAD: a high-extinction-ratio, achromatic, temperature-insensitive, high-damage-threshold, all-fiber, power-selective filter. In CLEO: 2011-Laser Science to Photonic Applications.
• Jeong, Y., Nilsson, J., Soh, D., Codemard, C. A., Dupriez, P., Farrell, C., Sahu, J. K., Kim, J., Yoo, S., Richardson, D. J., & others, . (2006). High power single-frequency Yb doped fiber amplifiers. In 2006 Optical Fiber Communication Conference and the National Fiber Optic Engineers Conference.
• Kim, J., Dupriez, P., Soh, D., Codemard, C., Yoo, S., Jeong, Y., Nilsson, J., & Sahu, J. K. (2006). Depressed clad hollow optical fiber with fundamental LP 01 mode cut-off. In Fiber Lasers III: Technology, Systems, and Applications, 6102.

Others

• Soh, D. (2024). Hardware authentication and monitoring using a super-resolution-imaging physical unclonable function..
• Soh, D., & Bisson, S. E. (2022). Systems and methods for quantum optical device authentication.
• Soh, D., Eichenfield, M., & Long, C. M. (2022). Photonic integrated circuits for generating high-brightness squeezed light.
• Soh, D., & Eichenfield, M. (2021). Remote quantum state transfer for qubits with different frequencies.
• Sarovar, M., Farley, D., Soh, D. B., Camacho, R., & Brif, C. (2019). Secure fiber optic seals enabled by quantum optical communication concepts.
• DeRose, C., Sarovar, M., Soh, D. B., Lentine, A., Davids, P., & Camacho, R. (2018). Transceivers and receivers for quantum key distribution and methods pertaining thereto.
• Moore, S., & Soh, D. B. (2018). Narrow bandwidth detection of vibration signature using fiber lasers.
• Soh, D. B., Sarovar, M., & Camacho, R. (2017). Self-referenced continuous-variable quantum key distribution.
• Tong, S., Prawiharjo, J., Cong, H., Soh, D., West, L. C., & Lin, A. H. (2014). Generating laser pulses based on chirped pulse amplification.
• Soh, D., & Lin, A. H. (2011). Optical pulse amplification based on stimulated Raman scattering.
• Soh, D., & Lin, T. H. (2009). Dispersion compensated mode-locked pulsed lasers and optical amplifiers.
• Soh, D. (2005). Advanced waveguides for high power optical fibre sources.