Environmental noise and disorder play a critical role in quantum particle and wave transport in complex media, including solid-state and biological systems. Recent work has predicted that coupling between noisy environments and disordered systems, in which coherent transport has been arrested due to localization effects, could actually enhance transport. Photonic integrated circuits are promising platforms for studying such effects, with a central goal being the development of large systems providing low-loss, high-fidelity control over all parameters of the transport problem. Here, we fully map out the role of static and dynamic disorder in quantum transport using a low-loss, phase-stable, nanophotonic processor consisting of a mesh of 56 generalized beamsplitters programmable on microsecond timescales. Over 85,600 transport experiments, we observe several distinct transport regimes, including environment-enhanced transport in strong, statically disordered systems. Low loss and programmability make this nanophotonic processor a promising platform for many-boson quantum simulation experiments.Quantum walks (QWs), the coherent analogy to classical random walks, have emerged as a useful model for experimental simulations of quantum transport (QT) phenomena in physical systems. QWs have been implemented in platforms including trapped ions 1,2 , ultra-cold atoms 3 , bulk optics 4-8 and integrated photonics 4,9-16 . Integrated photonic implementations are particularly attractive for relatively large coherence lengths, high interferometric visibilities, integration with single-photon sources 17,18 and detectors 19 , and the promise of scaling to many active and reconfigurable components. The role of static and dynamic disorder in the transport of quantum walkers has been of particular interest in the field of quantum simulation 20,21 .Control over static (time-invariant) and dynamic (timevarying) disorder enables studies of fundamentally interesting and potentially useful QT phenomena in discrete-time (DT) QWs. In systems with strong dynamic disorder, illustrated in Fig. 1(a), a quantum walker evolving over T time steps travels a distance proportional to √ T ; the coherent nature of the quantum walker is effectively erased, resulting in classical, diffusive transport characteristics 22,23 . In contrast, a quantum walker (or coherent wave) traversing an ordered system travels a distance proportional to T as a result of coherent interference between superposition amplitudes -a regime known as ballistic transport (see Fig. 1(b)). Perhaps most notably, a quantum walker propagating through a system with strong, static disorder becomes exponentially localized in space and time, inhibiting transport, as illustrated in Fig. 1(c). This QT phenomena is known as Anderson localization 24 and it has been observed in several systems, including optical media [9][10][11]25,26 . For systems in which transport has been arrested due to Anderson localization, it has recently been predicted that adding environmental noise (dynamic disord...

The force exerted by photons is of fundamental importance in light-matter interactions. For example, in free space, optical tweezers have been widely used to manipulate atoms and microscale dielectric particles. This optical force is expected to be greatly enhanced in integrated photonic circuits in which light is highly concentrated at the nanoscale. Harnessing the optical force on a semiconductor chip will allow solid state devices, such as electromechanical systems, to operate under new physical principles. Indeed, recent experiments have elucidated the radiation forces of light in high-finesse optical microcavities, but the large footprint of these devices ultimately prevents scaling down to nanoscale dimensions. Recent theoretical work has predicted that a transverse optical force can be generated and used directly for electromechanical actuation without the need for a high-finesse cavity. However, on-chip exploitation of this force has been a significant challenge, primarily owing to the lack of efficient nanoscale mechanical transducers in the photonics domain. Here we report the direct detection and exploitation of transverse optical forces in an integrated silicon photonic circuit through an embedded nanomechanical resonator. The nanomechanical device, a free-standing waveguide, is driven by the optical force and read out through evanescent coupling of the guided light to the dielectric substrate. This new optical force enables all-optical operation of nanomechanical systems on a CMOS (complementary metal-oxide-semiconductor)-compatible platform, with substantial bandwidth and design flexibility compared to conventional electrical-based schemes.

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We design a resistive heater optimized for efficient and low-loss optical phase modulation in a silicon-on-insulator (SOI) waveguide and characterize the fabricated devices. Modulation is achieved by flowing current perpendicular to a new ridge waveguide geometry. The resistance profile is engineered using different dopant concentrations to obtain localized heat generation and maximize the overlap between the optical mode and the high temperature regions of the structure, while simultaneously minimizing optical loss due to free-carrier absorption. A 61.6 µm long phase shifter was fabricated in a CMOS process with oxide cladding and two metal layers. The device features a phase-shifting efficiency of 24.77 ± 0.43 mW/π and a -3 dB modulation bandwidth of 130.0 ± 5.59 kHz; the insertion loss measured for 21 devices across an 8-inch wafer was only 0.23 ± 0.13 dB. Considering the prospect of densely integrated photonic circuits, we also quantify the separation necessary to isolate thermo-optic devices in the standard 220 nm SOI platform.