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Graphs have provided an expressive mathematical tool to model quantum-mechanical devices and systems. In particular, it has been recently discovered that graph theory can be used to describe and design quantum components, devices, setups and systems, based on the two-dimensional lattice of parametric nonlinear optical crystals and linear optical circuits, different to the standard quantum photonic framework. Realizing such graph-theoretical quantum photonic hardware, however, remains extremely challenging experimentally using conventional technologies. Here we demonstrate a graph-theoretical programmable quantum photonic device in very-large-scale integrated nanophotonic circuits. The device monolithically integrates about 2,500 components, constructing a synthetic lattice of nonlinear photon-pair waveguide sources and linear optical waveguide circuits, and it is fabricated on an eight-inch silicon-on-insulator wafer by complementary metal–oxide–semiconductor processes. We reconfigure the quantum device to realize and process complex-weighted graphs with different topologies and to implement different tasks associated with the perfect matching property of graphs. As two non-trivial examples, we show the generation of genuine multipartite multidimensional quantum entanglement with different entanglement structures, and the measurement of probability distributions proportional to the modulus-squared hafnian (permanent) of the graph’s adjacency matrices. This work realizes a prototype of graph-theoretical quantum photonic devices manufactured by very-large-scale integration technologies, featuring arbitrary programmability, high architectural modularity and massive manufacturing scalability.A graph-theoretical programmable quantum photonic device composed of about 2,500 components is fabricated on a silicon substrate within a 12 mm × 15 mm footprint. It shows the generation, manipulation and certification of genuine multiphoton multidimensional entanglement, as well as the implementations of scattershot and Gaussian boson sampling.

Operation speed and coherence time are two core measures for the viability of a qubit. Strong spin-orbit interaction (SOI) and relatively weak hyperfine interaction make holes in germanium (Ge) intriguing candidates for spin qubits with rapid, all-electrical coherent control. Here we report ultrafast single-spin manipulation in a hole-based double quantum dot in a germanium hut wire (GHW). Mediated by the strong SOI, a Rabi frequency exceeding 540 MHz is observed at a magnetic field of 100 mT, setting a record for ultrafast spin qubit control in semiconductor systems. We demonstrate that the strong SOI of heavy holes (HHs) in our GHW, characterized by a very short spin-orbit length of 1.5 nm, enables the rapid gate operations we accomplish. Our results demonstrate the potential of ultrafast coherent control of hole spin qubits to meet the requirement of DiVincenzo’s criteria for a scalable quantum information processor. Hole-spin qubits in germanium are promising candidates for rapid, all-electrical qubit control. Here the authors report Rabi oscillations with the record frequency of 540 MHz in a hole-based double quantum dot in a germanium hut wire, which is attributed to strong spin-orbit interaction of heavy holes.

The electric-field-induced superconducting properties of MoS 2 are investigated by means of magneto-transport measurements, uncovering evidence of spin–momentum locking. Symmetry-breaking has been known to play a key role in non-centrosymmetric superconductors with strong spin–orbit interactions (SOIs; refs  1 , 2 , 3 , 4 , 5 , 6 ). The studies, however, have been so far mainly focused on a particular type of SOI, known as the Rashba SOI (ref.  7 ), whereby the electron spin is locked to its momentum at a right-angle, thereby leading to an in-plane helical spin texture. Here we discuss electric-field-induced superconductivity in molybdenum disulphide (MoS 2 ), which exhibits a fundamentally different type of intrinsic SOI, manifested by an out-of-plane Zeeman-type spin polarization of energy valleys 8 , 9 , 10 . We find an upper critical field of approximately 52 T at 1.5 K, which indicates an enhancement of the Pauli limit by a factor of four as compared to that in centrosymmetric conventional superconductors. Using realistic tight-binding calculations, we reveal that this unusual behaviour is due to an inter-valley pairing that is symmetrically protected by Zeeman-type spin–valley locking against external magnetic fields. Our study sheds light on the interplay of inversion asymmetry with SOIs in confined geometries, and its role in superconductivity.

Graphene-based photonic devices, such as ultrafast photodetectors, optical modulators and tunable surface plasmon polariton devices, have experienced rapid development in recent years 1 , 2 , 3 , 4 , 5 , 6 because they benefit greatly from graphene's strong field-controlled optical response 7 , 8 . Here, we demonstrate a graphene/silicon-heterostructure photodiode formed by integrating graphene onto a silicon optical waveguide on a silicon-on-insulator (SOI) with a near to mid-infrared operational range. The waveguide enables absorption of evanescent light that propagates parallel to the graphene sheet, which results in a responsivity as high as 0.13 A W −1 at a 1.5 V bias for 2.75 µm light at room temperature. A photocurrent dependence on bias polarity was observed and attributed to two distinct mechanisms for optical absorption, that is, direct and indirect transitions in graphene at 1.55 µm and 2.75 µm, respectively. Our result demonstrates the use of in-plane absorption in a graphene-monolayer structure and the feasibility of exploiting indirect transitions in graphene/silicon-heterostructure waveguides for mid-infrared detection. A CMOS-compatible graphene/silicon-heterostructure photodetector formed by integrating graphene onto a silicon optical waveguide on silicon-on-insulator and operating in the near- and mid-infrared regions is demonstrated. A responsivity as high as 0.13 A W −1 is obtained at a bias of 1.5 V for 2.75-μm light at room temperature.

Given its potential for integration and scalability, silicon is likely to be a key platform for large-scale quantum technologies. Individual electron-encoded artificial atoms, formed by either impurities or quantum dots, have emerged as a promising solution for silicon-based integrated quantum circuits. However, single qubits featuring an optical interface, which is needed for long-distance exchange of information, have not yet been isolated in silicon. Here we report the isolation of single optically active point defects in a commercial silicon-on-insulator wafer implanted with carbon atoms. These artificial atoms exhibit a bright, linearly polarized single-photon emission with a quantum efficiency of the order of unity. This single-photon emission occurs at telecom wavelengths suitable for long-distance propagation in optical fibres. Our results show that silicon can accommodate single isolated optical point defects like in wide-bandgap semiconductors, despite a small bandgap (1.1 eV) that is unfavourable for such observations. Carbon-related point defects can be isolated in a commercial silicon-on-insulator wafer, acting as artificial atoms that provide efficient polarized single-photon emission at wavelengths suitable for long-distance propagation in optical fibres.

A central goal for quantum technologies is to develop platforms for precise and scalable control of individually addressable artificial atoms with efficient optical interfaces. Color centers in silicon, such as the recently-isolated carbon-related G-center, exhibit emission directly into the telecommunications O-band and can leverage the maturity of silicon-on-insulator photonics. We demonstrate the generation, individual addressing, and spectral trimming of G-center artificial atoms in a silicon-on-insulator photonic integrated circuit platform. Focusing on the neutral charge state emission at 1278 nm, we observe waveguide-coupled single photon emission with narrow inhomogeneous distribution with standard deviation of 1.1 nm, excited state lifetime of 8.3 ± 0.7 ns, and no degradation after over a month of operation. In addition, we introduce a technique for optical trimming of spectral transitions up to 300 pm (55 GHz) and local deactivation of single artificial atoms. This non-volatile spectral programming enables alignment of quantum emitters into 25 GHz telecommunication grid channels. Our demonstration opens the path to quantum information processing based on implantable artificial atoms in very large scale integrated photonics. Realising integrated photonic circuits containing isolated telecommunications-wavelength artificial atom single photon emitters is an outstanding challenge in quantum technologies. Here, the authors demonstrate how to embed optically tunable G-centers in silicon-on-insulator integrated circuits.

Global quantum networks will benefit from the reliable fabrication and control of high-performance solid-state telecom photon-spin interfaces. T radiation damage centres in silicon provide a promising photon-spin interface due to their narrow O-band optical transition near 1326 nm and long-lived electron and nuclear spin lifetimes. To date, these defect centres have only been studied as ensembles in bulk silicon. Here, we fabricate high concentration T centre ensembles in the 220 nm device layer of silicon-on-insulator wafers by ion implantation and subsequent annealing. We then develop a method that uses spin-dependent optical transitions to benchmark the characteristic optical spectral diffusion within these T centre ensembles. Using this new technique, we show that with minimal optimization to the fabrication process high densities of implanted T centres localized ≲100 nm from an interface display ∼1 GHz characteristic levels of total spectral diffusion.

Complementary field-effect transistors—which have n-type and p-type field-effect transistors (FETs) vertically stacked on top of each other—can boost area efficiency in integrated circuits. However, silicon-based complementary FETs suffer from several issues, including difficulty in balancing electron and hole mobility. Here we report heterogeneous complementary FETs that combine p-type FETs made with silicon-on-insulator technology and n-type FETs made with two-dimensional molybdenum disulfide (MoS 2 ). Through mobility matching and multiple-gate modulation of the MoS 2 , the mobility mismatch issue of fully silicon-based systems can be addressed. Our integration approach leverages the maturity of the silicon process, the low thermal budget of MoS 2 and the low aspect ratio of the device structures to reduce process complexity and device degradation. We use the approach to create a complementary FET inverter that exhibits a voltage gain of 142.3 at a supply voltage of 3 V, and a voltage gain of 1.2 and power consumption of 64 pW at a supply voltage of 100 mV. We also develop a four-inch fabrication process for the silicon–two-dimensional complementary FETs. By combining p-type transistors made with silicon-on-insulator technology and n-type transistors made with two-dimensional molybdenum disulfide, heterogeneous complementary field-effect transistors can be fabricated on the wafer scale.

Controlling large-scale many-body quantum systems at the level of single photons and single atomic systems is a central goal in quantum information science and technology. Intensive research and development has propelled foundry-based silicon-on-insulator photonic integrated circuits to a leading platform for large-scale optical control with individual mode programmability. However, integrating atomic quantum systems with single-emitter tunability remains an open challenge. Here, we overcome this barrier through the hybrid integration of multiple InAs/InP microchiplets containing high-brightness infrared semiconductor quantum dot single photon emitters into advanced silicon-on-insulator photonic integrated circuits fabricated in a 300 mm foundry process. With this platform, we achieve single-photon emission via resonance fluorescence and scalable emission wavelength tunability. The combined control of photonic and quantum systems opens the door to programmable quantum information processors manufactured in leading semiconductor foundries. Integrating tunable quantum emitters with commercial photonic circuits is promising for quantum information applications but remains a challenge. Here the authors report integration of InAs/InP microchiplets containing quantum dot single photon emitters into a large-scale foundry silicon platform.

In this article, we present an ultra-wideband, fully-differential quadrature signal generation network for 5G applications. The ultra-wideband network is composed of a passive balun and cascaded transformer-based quadrature hybrid. Passive balun converts a single-ended signal to differential with minimum insertion loss, and transformer-based quadrature hybrids are cascaded to suppress I/Q imbalance over an ultra-wide bandwidth. The coupling coefficient of the transformer-based quadrature hybrid is enhanced by adopting vertically stacked multiturn transformer topology to extend operation bandwidth and reduce passive loss and chip area. A novel layout and signal routings are proposed to reduce passive loss, undesired magnetic coupling and I/Q imbalance, making meander lines for phase matching unnecessary. The proposed ultra-wideband quadrature signal generation network is designed in GlobalFoundries 45 nm CMOS SOI process with a core area of 845 μm × 495 μm. The output I/Q magnitude mismatch is less than 0.5 dB from 16 to 60 GHz, and phase mismatch is less than 2° from 16.5 to 54.7 GHz. The input return loss is lower than −10 dB from 22 to 45 GHz, and signal loss varies from 5.74 to 7.4 dB (including 1:2 power splitting and loss from passive balun). The effective image rejection ratio (IRR) is calculated based on I/Q mismatch and is higher than 40 dB from 21.5 to 53.5 GHz.