# Hideo Mabuchi's research while affiliated with Stanford University and other places

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## Publications (232)

Silicon is a common material for photonics due to its favorable optical properties in the telecom and mid-wave IR bands, as well as compatibility with a wide range of complementary metal-oxide semiconductor (CMOS) foundry processes. Crystalline inversion symmetry precludes silicon from natively exhibiting second-order nonlinear optical processes. I...

Thin-film lithium niobate (TFLN) is an emerging platform for compact, low-power nonlinear-optical devices, and has been used extensively for near-infrared frequency conversion. Recent work has extended these devices to mid-infrared wavelengths, where broadly tunable sources may be used for chemical sensing. To this end, we demonstrate broadband dif...

The realization of deterministic photon-photon gates is a central goal in optical quantum computation and engineering. While solid-state nonlinear optics offers a scalable, room temperature solution, weak material nonlinearities lead to extremely demanding requirements on optical loss and confinement, which to date have not been realized. In this w...

We show that the nonlinear stochastic dynamics of a measurement-feedback-based coherent Ising machine (MFB-CIM) in the presence of quantum noise can be exploited to sample degenerate ground and low-energy spin configurations of the Ising model. We formulate a general discrete-time Gaussian-state model of the MFB-CIM, which faithfully captures the n...

We demonstrate efficient m id-infrared d ifference-frequency g eneration in dispersion-engineered thin-film lithium niobate ridge waveguides on sapphire. These uniformly poled devices achieve phase-matching bandwidths in excess of a micron, and rapid phase-matching peak tuning with temperature.

We demonstrate electric-field-induced second-harmonic generation from 2 . 4 μm to 1 . 2 μm in 3 μm-thick silicon ridge waveguides integrated with alternating p-n diodes. Second-harmonic generation as a function of fundamental wavelength tuning is characterized.

We present a split-step framework for simulating nonlinear propagation of multimode quantum noise and entanglement in ultrafast pulses, beyond conventional linearized-noise approximations. We apply our method to model state-of-the-art dispersion-engineered devices on thin-film lithium niobate.

We study the emergence of non-Gaussian quantum features in pulsed squeezed light generation with a mesoscopic number (i.e., dozens to hundreds) of pump photons. Due to the strong optical nonlinearities necessarily involved in this regime, squeezing occurs alongside significant pump depletion, compromising the predictions made by conventional semicl...

Ultra-short pulses propagating in nonlinear nanophotonic waveguides can simultaneously leverage both temporal and spatial field confinement, promising a route towards single-photon nonlinearities in an all-photonic platform. In this multimode quantum regime, however, faithful numerical simulations of pulse dynamics naively require a representation...

Periodically poled thin-film lithium niobate (TFLN) waveguides have emerged as a leading platform for highly efficient frequency conversion in the near-infrared. However, the commonly used silica bottom-cladding results in high absorption loss at wavelengths beyond 2.5 µm. In this work, we demonstrate efficient frequency conversion in a TFLN-on-sap...

Periodically poled thin-film lithium niobate (TFLN) waveguides have emerged as a leading platform for highly efficient frequency conversion in the near-infrared. However, the commonly used silica bottom-cladding results in high absorption loss at wavelengths beyond 2.5 $\mu$m. In this work, we demonstrate efficient frequency conversion in a TFLN-on...

We show that the nonlinear stochastic dynamics of a measurement-feedback-based coherent Ising machine (MFB-CIM) in the presence of quantum noise can be exploited to sample degenerate ground and low-energy spin configurations of the Ising model. We formulate a general discrete-time Gaussian-state model of the MFB-CIM which faithfully captures the no...

The advent of dispersion-engineered and highly nonlinear nanophotonics is expected to open up an all-optical path towards the strong-interaction regime of quantum optics by combining high transverse field confinement with ultra-short-pulse operation. Obtaining a full understanding of photon dynamics in such broadband devices, however, poses major c...

Ultra-short pulses propagating in nonlinear nanophotonic waveguides can simultaneously leverage both temporal and spatial field confinement, promising a route towards single-photon nonlinearities in an all-photonic platform. In this multimode quantum regime, however, faithful numerical simulations of pulse dynamics naïvely require a representation...

We demonstrate frequency conversion in the mid-IR using periodically poled lithium niobate thin-film ridge waveguides on sapphire. These devices are characterized by measuring the transfer-functions, and the normalized conversion efficiencies for second- harmonic and difference-frequency generations.

We introduce a theoretical framework based on Fano's theory of discrete-continuum interactions to analyze the quantum dynamics of broadband parametric downconversion (PDC) in the few-pump-photon regime of nonlinear quantum nanophotonics. Applying this unified analytic approach to 1D $\chi^{(2)}$-nonlinear waveguides, we find a host of remarkable dy...

We demonstrate voltage-tunable thermo-optic bi- and tristability in silicon photonic microring resonators with lateral p-i-n junctions and present a technique for characterizing the thermo-optic transient response of integrated optical resonators. Our method for thermo-optic transient response measurement is applicable to any integrated photonics p...

We propose a deterministic, measurement-free implementation of a cubic phase gate for continuous- variable quantum information processing. In our scheme, the applications of displacement and squeezing operations allow us to engineer the effective evolution of the quantum state propagating through an optical Kerr nonlinearity. Under appropriate cond...

We demonstrate voltage-tunable thermo-optic bi- and tri-stability in silicon photonic microring resonators with lateral p-i-n junctions and present a technique for characterizing the thermo-optic transient response of integrated optical resonators. Our method for thermo-optic transient response measurement is applicable to any integrated photonics...

Electric dipole radiation can be controlled by engineering of the photonic environment. A coherent interaction between forward and backward emission depends interferometrically on the position of a nearby mirror. The transverse coherence of exciton emission in a single layer of MoSe2 and the highly radiatively broadened nature of our samples remove...

We propose a measurement-free construction of a cubic phase gate based on a Kerr nonlinearity and Gaussian transformations. Experimental feasibility is discussed for pulsed nanophotonic waveguides where quantum states are encoded into quantum solitons.

We propose a deterministic, measurement-free implementation of a cubic phase gate for continuous-variable quantum information processing. In our scheme, the applications of displacement and squeezing operations allow us to engineer the effective evolution of the quantum state propagating through an optical Kerr nonlinearity. Under appropriate condi...

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 wave packet corresponding to center-of-mass motion and an orbital state corresponding to the motion of the electron and hole abo...

We propose a theoretical scheme to deterministically generate Fock states in a Kerr cavity through adiabatic variation of the driving field strength and the cavity detuning. We show that the required time to generate an n-photon Fock state scales as the square root of n. Requirements for the Kerr coefficient relative to the system decoherence rate...

We propose an integrated photonic circuit that acts as an optical coherent Ising machine and simulate its performance on some example problems. In contrast to previous all-optical approaches, the proposed integrated Ising machine does not require an optical parametric oscillator and can hence operate at a single wavelength, reducing the overall des...

We present a new scheme to efficiently establish entanglement between optical modes in a time-multiplexed coherent Ising machine (CIM) by means of nonlocal measurement and feedback. We numerically simulate and evaluate the generation of steady-state entanglement in a system with nearest-neighbor interactions on a 1D ring, and we compare the results...

We present a new scheme to efficiently establish entanglement between optical modes in a time-multiplexed coherent Ising machine (CIM) by means of nonlocal measurement and feedback. We numerically simulate and evaluate the generation of steady-state entanglement in a system with nearest-neighbor interactions on a 1D ring, and we compare the results...

Physical annealing systems provide heuristic approaches to solving combinatorial optimization problems. Here, we benchmark two types of annealing machines—a quantum annealer built by D-Wave Systems and measurement-feedback coherent Ising machines (CIMs) based on optical parametric oscillators—on two problem classes, the Sherrington-Kirkpatrick (SK)...

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...

The measurement of inhomogeneous conductivity in optically crystallized, amorphous Ge 2 Sb 2 Te 5 (GST) films is demonstrated via scanning microwave impedance microscopy (MIM). Qualitative consistency with expectations is demonstrated in spots crystallized by focused coherent light at various intensities, exposure times, and film thicknesses. The c...

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...

Electric dipole radiation can be controlled by coherent optical feedback, as has previously been studied by modulating the photonic environment for point dipoles placed both in optical cavities and near metal mirrors. In experiments involving fluorescent molecules, trapped ions and quantum dots the point nature of the dipole, its sub-unity quantum...

We propose a theoretical scheme to deterministically generate Fock states in a Kerr cavity thorough adiabatic variation of the driving field strength and the cavity detuning. We show that the required time to generate a $n$-photon Fock state scales as the square root of $n$. Requirements for the Kerr coefficient relative to the system decoherence r...

The quantum features of ultrashort-pulse optical parametric oscillators (OPOs) are theoretically investigated in the nonlinear regime near and above threshold. Starting from basic premises of input-output theory, we derive a general quantum model for pulsed OPOs subject to $\chi^{(2)}$ interactions between a multimode signal cavity and a non-resona...

The quantum features of ultrashort-pulse optical parametric oscillators (OPOs) are theoretically investigated in the nonlinear regime near and above threshold. Starting from basic premises of input-output theory, we derive a general quantum model for pulsed OPOs subject to χ(2) interactions between a multimode signal cavity and a non-resonant broad...

We elucidated the mechanism of supercritical Hopf bifurcation in the semi-classical Maxwell–Bloch equations for cavity quantum electrodynamics by formulating the atom–field interaction as a feedback control system. It turns out that the existence of self-oscillatory states is a rather unexpected manifestation of the atomic pseudospin precession dyn...

Physical annealing systems provide a heuristic approach to solve NP-hard Ising optimization problems. It is believed that the connectivity between spins in such annealers significantly impacts the machine's computational effectiveness. In this paper we study the performance of two types of annealing machines that have very different connectivity --...

Physical annealing systems provide a heuristic approach to solve NP-hard Ising optimization problems. It is believed that the connectivity between spins in such annealers significantly impacts the machine's computational effectiveness. In this paper we study the performance of two types of annealing machines that have very different connectivity --...

We report on a laser annealing procedure which greatly improves the quality of suspended monolayers of chemical vapor deposition (CVD) grown MoSe2. Annealing with a green laser locally heats the suspended flake to approximately 600 K, which both removes contaminants and reduces strain gradients. At 4 K, we observe linewidths as narrow as 3.5 meV (1...

Few techniques are suited to probe the structure and dynamics of molecular complexes at the mesoscale level (∼100-1000 nm). We have developed a single-molecule technique that uses tracking fluorescence correlation spectroscopy (tFCS) to probe the conformation and dynamics of mesoscale molecular assemblies. tFCS measures the distance fluctuations be...

We consider the transfer functions describing the input-output relation for a class of linear open quantum systems involving feedback with nonzero time delays. We show how such transfer functions can be factorized into a product of terms which are transfer functions of canonical physically realizable components. We prove under certain conditions th...

We introduce a theoretical scheme for generating Fock states using a Kerr cavity by adiabatic variation of the detuning and driving field amplitude. We perform numerical calculations to determine requirements for experimental feasibility.

Decades of study of the RNA folding problem have revealed that diverse and complex structured RNAs are built from a common set of recurring structural motifs, leading to the perspective that a generalizable model of RNA folding may be developed from understanding of the folding properties of individual structural motifs. We used single-molecule flu...

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...

Decades of study of the architecture and function of structured RNAs have led to the perspective that RNA tertiary structure is modular, made of locally stable domains that retain their structure across RNAs. We formalize a hypothesis inspired by this modularity-that RNA folding thermodynamics and kinetics can be quantitatively predicted from separ...

Weakly nonlinear degrees of freedom in dissipative quantum systems tend to localize near manifolds of quasi-classical states. We present a family of analytical and computational methods for deriving optimal unitary model transformations based on representations of finite dimensional Lie groups. The transformations are optimal in that they minimize...

Biomolecular systems such as multiprotein complexes or biopolymers can span several tens to several hundreds of nanometers, but the dynamics of such “mesocale” molecules remain challenging to probe. We have developed a single-molecule technique that uses Tracking Fluorescence Correlation Spectroscopy (tFCS) to measure the conformation and dynamics...

We show that coherent feedback control can transfer optical nonlinearities from a single-wavelength, bistable Kerr cavity into a tunable range of wavelengths when coupled to a non-degenerate parametric oscillator under threshold.

We present microscopically resolved, polarized spectroscopy of Raman scattering collected from tetragonal SrTiO3. The anisotropic response of first-order Raman peaks within a single tetragonal domain has been measured. From these data, we assign symmetries to the phonons seen in the first-order Raman spectrum which is normally complicated by uncont...

Unconventional, special-purpose machines may aid in accelerating the solution of some of the hardest problems in computing, such as large-scale combinatorial optimizations, by exploiting different operating mechanisms than standard digital computers. We present a scalable optical processor with electronic feedback that can be realized at large scal...

We develop reduced models that describe half-harmonic generation in a synchronously-pumped optical parametric oscillator above threshold, where nonlinearity, dispersion, and group-velocity mismatch are all relevant. These models are based on (1) an eigenmode expansion for low pump powers, (2) a simulton-like sech-pulse ansatz for intermediate power...

The past decade has seen a wealth of 3D structural information about complex structured RNAs and identification of functional intermediates. Nevertheless, developing a complete and predictive understanding of the folding and function of these RNAs in biology will require connection of individual rate and equilibrium constants to structural changes...

A network of optical parametric oscillators is used to simulate classical Ising and XY spin chains. The collective nonlinear dynamics of this network, driven by quantum noise rather than thermal fluctuations, seeks out the Ising / XY ground state as the system transitions from below to above the lasing threshold. We study the behavior of this "Isin...

We present a comprehensive analysis of 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...

Due to their strong light conﬁnement, waveguides with optical nonlinearities may be a promising platform for energy-eﬃcient optical computing. Slow light can enhance a waveguide’s eﬀective nonlinearity, which could result in devices that operate in low-power regimes where quantum ﬂuctuations are important, and may also have quantum applications inc...

Networks of open quantum systems with feedback have become an active area of
research for applications such as quantum control, quantum communication and
coherent information processing. A canonical formalism for the interconnection
of open quantum systems using quantum stochastic differential equations (QSDEs)
has been developed by Gough, James an...

We show that the ability to make direct measurements of momentum, in addition to the usual direct measurements of position, allows a simple configuration of two identical mechanical oscillators to be used for broadband back-action-free force metrology. This would eliminate the need for an optical reference oscillator in the scheme of Tsang and Cave...

We propose reduced-order models based on eigenmodes and manifold projection to study synchronously pumped optical parametric oscillators. This enables rapid simulation and gives physical insight to the pulse compression and sech-pulse formation observed in experiments.

Matlab script for afm image analysis.
DOI:
http://dx.doi.org/10.7554/eLife.12790.015

The purpose of this paper is to study the problem of generalizing the Belavkin-Kalman filter to the case where the classical measurement signal is replaced by a fully quantum non-commutative output signal. We formulate a least mean squares estimation problem that involves a non-commutative system as the filter processing the non-commutative output...

At strong pump powers, a semiconductor optical cavity passes through a Hopf
bifurcation and undergoes self-oscillation. We simulate this device using
semiclassical Langevin equations and assess the effect of quantum fluctuations
on the dynamics. Below threshold, the cavity acts as a phase-insensitive linear
amplifier, with noise $\sim 5\times$ larg...

This paper derives Langevin equations for an optical cavity where the
dominant nonlinearity arises from free-carrier dispersion. We define a
generalized Wigner function, compute a Fokker-Planck equation that approximates
the master equation, and convert this to a system of stochastic differential
equations. These equations are similar to the Wigner...

Background
Single-molecule techniques have emerged as incisive approaches for addressing a wide range of questions arising in contemporary biological research [ 1-4]. The analysis and interpretation of raw single-molecule data benefits greatly from the ongoing development of sophisticated statistical analysis tools that enable accurate inference at...

We present nonlinear photonic circuit models for constructing programmable
linear transformations and use these to realize a coherent Perceptron, i.e., an
all-optical linear classifier capable of learning the classification boundary
iteratively from training data through a coherent feedback rule. Through
extensive semi-classical stochastic simulati...

Photonic circuits in which stateful components are coupled via guided
electromagnetic fields are natural candidates for native implementation of
iterative stochastic algorithms based on propagation of information around a
graph. Conversely, such message passing algorithms suggest novel circuit
architectures for signal processing and computation tha...

Nanoscale integrated photonic devices and circuits offer a path to ultra-low
power computation at the few-photon level. Here we propose an optical circuit
that performs a ubiquitous operation: the controlled, random-access readout of
a collection of stored memory phases or, equivalently, the computation of the
inner product of a vector of phases wi...