Controlling and programming quantum devices to process quantum information by the unit of quantum dit, i.e., qudit, provides the possibilities for noise-resilient quantum communications, delicate quantum molecular simulations, and efficient quantum computations, showing great potential to enhance the capabilities of qubit-based quantum technologies. Here, we report a programmable qudit-based quantum processor in silicon-photonic integrated circuits and demonstrate its enhancement of quantum computational parallelism. The processor monolithically integrates all the key functionalities and capabilities of initialisation, manipulation, and measurement of the two quantum quart (ququart) states and multi-value quantum-controlled logic gates with high-level fidelities. By reprogramming the configuration of the processor, we implemented the most basic quantum Fourier transform algorithms, all in quaternary, to benchmark the enhancement of quantum parallelism using qudits, which include generalised Deutsch-Jozsa and Bernstein-Vazirani algorithms, quaternary phase estimation and fast factorization algorithms. The monolithic integration and high programmability have allowed the implementations of more than one million high-fidelity preparations, operations and projections of qudit states in the processor. Our work shows an integrated photonic quantum technology for qudit-based quantum computing with enhanced capacity, accuracy, and efficiency, which could lead to the acceleration of building a large-scale quantum computer.

 Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

No abstract

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.

Because of rapid economic development and the increase in social demand, China has been suffering from serious air pollution, in particular, haze pollution. To mitigate haze from the source, it is essential to achieve co-control of three important haze precursors: volatile organic compounds (VOCs), sulfur dioxide (SO 2 ), and nitrogen oxide (NO x ). In this study, we used the environmentally extended input-output model, structural path analysis, and structural path decomposition method to investigate changes in consumption-based emissions of three major haze precursors (i.e., NO x , SO 2 , and VOCs) in China during 2007-2017. First, the results revealed that fixed capital formation was the most critical final demand to cocontrol the three precursors. Investment in construction was the most important behavior for co-control. Second, the most crucial common path driving the changes in emissions of the three precursors was "transportation and ware-housing→household consumption" during 2007-2012, and "electricity, gas, and water supply→household consumption" during 2012-2017. Finally, direct emission intensity of transportation and warehousing, and electricity, gas, and water supplies were critical to co-control precursors. The results of this study provided a comprehensive understanding of changes in haze precursor emissions driven by demand. Therefore, China must strengthen the co-control of multiple pollutant emissions on both the production and consumption sides by adjusting supply chains.

No abstract

Entanglement and topology both portray nature at the fundamental level but in different manners. Entangled states of quantum particles are intrinsically sensitive to environment, whereas topological phases of matters represent natural robustness against environmental perturbations. Harnessing topology physics to protect entanglement thus has a great potential for reliable quantum applications. However, generating topologically-protected entanglement remains a significant challenge, which requires operating complex quantum devices in combined extreme conditions. Here we report topologically-protected quantum entanglement emitters, that emit topological Einstein-Podolsky-Rosen entangled state and topological multiphoton entangled state from a monolithically-integrated plug-and-play silicon-photonic chip in ambient conditions. The device emulating a photonic anomalous Floquet insulator allows the generation of up to four-photon topological entangled states at nontrivial edge modes. More importantly, we show that the Einstein-Podolsky-Rosen entanglement emitters can be topologically protected against artificial structure defects, by comparing tomographically measured fidelities of 0.968 ± 0.004 and 0.951 ± 0.01 for the perfect and defected emitters, respectively. Our topologically-protected entanglement emitters may find applications in photonic quantum computation and quantum simulation, and in the study of quantum topological physics.

We designed, fabricated, and characterized a programmable qudit-based quantum processor on silicon and several quantum algorithms were implemented using qudits which shows the logarithmic speed-up, counting rate acceleration and accuracy improvement of the qudit processor.