Alexander Yu. Vlasov
Here is discussed the Hamiltonian approach to construction of deterministic universal (in approximate sense) programmable quantum circuits with qubits or any other quantum systems with dimension of Hilbert space is $n \ge 2$.
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Google recently announced that they had achieved quantum supremacy with 53 qubits (base-2 binaries or radix-2), corresponding to a computational state-space of dimension 253 (about 1016). Google claimed to perform computations that took 200 seconds on their quantum processor that would have taken 10,000 years to accomplish on a classical supercomputer [1]. However, achieving superposition and entanglement of 53 qubits is not an easy task given the environmental noise that decoheres the qubits. In this paper, we claim that one can potentially achieve a similar computational dimension with fewer…
We analyze and compare the optimality of approximate and probabilistic universal programmable quantum processors. We define several characteristics how to quantify the optimality and we study in detail performance of three types of programmable quantum processors based on (1) the C-NOT gate, (2) the SWAP operation, and (3) the model of the quantum information distributor - the QID processor. We show under which conditions the measurement assisted QID processor is optimal. We also investigate optimality of the so-called U-processors and we also compare the optimal approximative implementation o…
A quantum processor (the programmable gate array) is a quantum network with a fixed structure. A space of states is represented as tensor product of data and program registers. Different unitary operations with the data register correspond to "loaded" programs without any changing or "tuning" of network itself. Due to such property and undesirability of entanglement between program and data registers, universality of quantum processors is subject of rather strong restrictions. By different authors was developed universal "stochastic" quantum gate arrays. It was proved also, that "deterministic…
We present a probabilistic quantum processor for qudits. The processor itself is represented by a fixed array of gates. The input of the processor consists of two registers. In the program register the set of instructions (program) is encoded. This program is applied to the data register. The processor can perform any operation on a single qudit of the dimension N with a certain probability. If the operation is unitary, the probability is in general 1/N^2, but for more restricted sets of operators the probability can be higher. In fact, this probability can be independent of the dimension of t…
We consider a scheme of quantum teleportation where a receiver has multiple (N) output ports and obtains the teleported state by merely selecting one of the N ports according to the outcome of the sender's measurement. We demonstrate that such teleportation is possible by showing an explicit protocol where N pairs of maximally entangled qubits are employed. The optimal measurement performed by a sender is the square-root measurement, and a perfect teleportation fidelity is asymptotically achieved for a large N limit. Such asymptotic teleportation can be utilized as a universal programmable pro…
A quantum processor to import, process, and export optical quantum states is a common core technology enabling various photonic quantum information processing. However, there has been no photonic processor which is simultaneously universal, scalable, and programmable. Here, we report on an original loop-based single-mode versatile photonic quantum processor which is designed to be universal, scalable, and programmable. Our processor can perform arbitrarily many steps of programmable quantum operations on a given single-mode optical quantum state by time-domain processing in a dynamically contr…
In this paper is presented an abstract theory of quantum processors and controllers, special kind of quantum computational network defined on a composite quantum system with two parts: the controlling and controlled subsystems. Such approach formally differs from consideration of quantum control as some external influence on a system using some set of Hamiltonians or quantum gates. The model of programmed quantum controllers discussed in present paper is based on theory of universal deterministic quantum processors (programmable gate arrays). Such quantum devices may simulate arbitrary evoluti…
Even if Google AI's Sycamore processor is efficient for the particular task it has been designed for it fails to deliver universal computational capacity. Furthermore, even classical devices implementing transverse homoclinic orbits realize exponential speedups with respect to universal classical as well as quantum computations. Moreover, relative to the validity of quantum mechanics, there already exist quantum oracles which violate the Church-Turing thesis.
A universal qudit quantum processor with trapped ions
本文利用囚禁离子构建局部 Hilbert 空间维度最高达 7 的通用 qudit 量子处理器，在保持接近 qubit 处理器性能的同时，支持高维量子系统原生模拟及更高效的 qubit 算法实现。
20-Mode Universal Quantum Photonic Processor
本文报告了迄今最大规模的20模式通用量子光子处理器，能在20个输入模式上实现任意酉变换，具有高振幅保真度、低光损耗和高量子干涉可见度。
Resource-efficient universal photonic processor based on time-multiplexed hybrid architectures
本文提出了一种基于离散时间量子行走的通用光子处理器，通过将任意线性变换转换为量子行走的硬币和步骤算子，并映射到实验参数，实现了高效且可扩展的光子处理系统，同时展示了其对实验缺陷的高鲁棒性。
Medium-scale quantum devices that integrate about hundreds of physical qubits are likely to be developed in the near future. However, such devices will lack the resources for realizing quantum fault tolerance. Therefore, the main challenge of exploring the advantage of quantum computation is to minimize the impact of device and control imperfections without encoding. Quantum error mitigation is a solution satisfying the requirement. Here, we demonstrate an error mitigation protocol based on gate set tomography and quasiprobability decomposition. One- and two-qubit circuits are tested on a supe…
Demonstrating a universal logical gate set in error-detecting surface codes on a superconducting quantum processor
本研究针对超导系统中表面码逻辑量子比特两量子比特门缺失的问题，用处理器\textit{Wukong}在距离-2表面码上实现通用逻辑门集合，含横向CNOT与任意单量子比特旋转门，还容错制备逻辑贝尔态，证实纠缠，推动超导容错量子计算发展。
Photonic processors are pivotal for both quantum and classical information processing tasks using light. In particular, linear optical quantum information processing requires both largescale and low-loss programmable photonic processors. In this paper, we report the demonstration of the largest universal quantum photonic processor to date: a low-loss, 12-mode fully tunable linear interferometer with all-to-all coupling based on stoichiometric silicon nitride waveguides.
Experimental certification of contextuality, coherence and dimension in a programmable universal photonic processor
针对高维量子特性认证的指数复杂度难题，研究团队借助飞秒激光直写的六模可编程光子处理器，通过成对重叠测量实现了最高5维量子系统的相干性、维度见证量实验认证，验证了量子上下文性对量子问询任务优势的支撑作用，为集成光子平台的量子特性认证提供了高效新途径。
A possibility of performing the C-NOT gate operation at the ground and the first excited states of two harmonic oscillators interacting via a two-level system subject to complete control is demonstrated. The system resembles Turing machine, where the result of interaction between oscillators and the two level system is restricted to a certain fixed unitary transformation matrix, while all the control required for the implementation of the gate is provided via manipulations with the two-level system, which remains the only fully-controllable part of the entire system. Each gate operation requir…
A single programmable photonic circuit for universal quantum measurements
本文提出一种可编程测量处理器，实现任意量子测量，通过大规模集成光子架构实现高精度相干控制，验证了其在量子态鉴别、状态估计和随机性生成中的优越性能。
Interaction-free measurement of multiple objects using a universal integrated photonic processor
本文提出利用单个量子探针在云平台Ascella光子处理器上实现多物体的交互无测量，展示了单光子对五个物体的连续检测，扩展了原始单物体交互无测量方案。
Implementation of a scalable universal two-qubit quantum processor with electron and nuclear spins in a trapped ion
本文提出利用离子内部能级和电子/核自旋实现可扩展 n 离子-2n 量子比特处理器，并在单离子系统上验证通用门与 Grover 算法，为大幅扩展量子计算 Hilbert 空间提供新路径。
Measuring central charge on a universal quantum processor
本文利用 IBM 通用量子处理器、变分量子电路与误差缓解技术制备临界自旋链基态，并通过 Rényi-Shannon 熵次导项标度首次实验测定中心荷，结果与 TFI 和 XXZ 模型吻合。
The universal quantum computer is a device capable of simulating any physical system and represents a major goal for the field of quantum information science. Algorithms performed on such a device are predicted to offer significant gains for some important computational tasks. In the context of quantum information, "universal" refers to the ability to perform arbitrary unitary transformations in the system's computational space. The combination of arbitrary single-quantum-bit (qubit) gates with an entangling two-qubit gate is a gate set capable of achieving universal control of any number of q…
A universal quantum processor is a device that takes as input a (quantum) program, containing an encoding of an arbitrary unitary gate, and a (quantum) data register, on which the encoded gate is applied. While no perfect universal quantum processor can exist, approximate processors have been proposed in the past two decades. A fundamental open question is how the size of the smallest quantum program scales with the approximation error. Here we answer the question, by proving a bound on the size of the program and designing a concrete protocol that attains the bound in the asymptotic limit. Ou…
Quantum devices, from simple fixed-function tools to the ultimate goal of a universal quantum computer, will require high quality, frequent repetition of a small set of core operations, such as the preparation of entangled states. These tasks are perfectly suited to realisation by a co-processor or supplementary instruction set, as is common practice in modern CPUs. In this paper, we present two quintessentially quantum co-processor functions: production of a GHZ state, and implementation of optimal universal (asymmetric) quantum cloning. Both are based on the evolution of a fixed Hamiltonian.…
Most modern classical processors support so-called von Neumann architecture with program and data registers. In present work is revisited similar approach to models of quantum processors. Deterministic programmable quantum gate arrays are considered as an example. They are also called von Neumann quantum processors here and use conditional quantum dynamics. Such devices have some problems with universality, but consideration of hybrid quantum processors, i.e., models with both continuous and discrete quantum variables resolves the problems. It is also discussed comparison of such a model of qu…
Realization of high-fidelity perfect entangler between remote superconducting quantum processors
本文利用同轴电缆驻波模式在30厘米距离的远程超导量子处理器间实现了CNOT和CZ高保真完美纠缠门，保真度分别达99.15%和98.04%，为大规模分布式量子计算奠定了基础。
We consider an exact state transmission, where a density matrix in one information processor A at time $t=0$ is exactly equal to that in another processor B at a later time. We demonstrate that there always exists a complete set of orthogonal states, which can be employed to perform the exact state transmission. Our result is very general in the sense that it holds for arbitrary media between the two processors and for any time interval. We illustrate our results in terms of models of spin, fermionic and bosonic chains. This complete set can be used as bases to study the perfect state transfer…
Arbitrary quantum circuits on a fully integrated two-qubit computation register for a trapped-ion quantum processor
本文在基于量子电荷耦合器件架构的囚禁离子处理器中，利用芯片集成微波寻址在 ^9Be^+ 双离子晶体上实现通用门集与任意双量子比特电路，并表征串扰和门性能。
A universal programmable Gaussian Boson Sampler for drug discovery
本研究构建了通用可编程的时间片编码GBS光子量子处理器，实现32节点图团簇查找性能约为经典采样两倍，还成功用于分子对接与RNA折叠预测两种药物发现任务，推动GBS走向实际应用。
We show that it is possible to control the trade-off between information gain and disturbance in generalized measurements of qudits by utilizing the programmable quantum processor. This universal quantum machine allows us to perform a generalized measurement on the initial state of the input qudit to construct a Husimi function of this state. The trade-off between the gain and the disturbance of the qudit is controlled by the initial state of ancillary system that acts as a program register for the quantum-information distributor. The trade-off fidelity does not depend on the initial state of …
We present a systematic analysis how one can improve performance of probabilistic programmable quantum processors. We generalize a simple Vidal-Masanes-Cirac processor that realizes U(1) rotations on a qubit with the phase of the rotation encoded in a state of the program register. We show how the probability of success of the probabilistic processor can be enhanced by using the processor in loops. In addition we show that the same strategy can be utilized for a probabilistic implementation of non-unitary transformations on qubits. In addtion, we show that an arbitrary SU(2) transformations of…
A universal programmable quantum processor uses program quantum states to apply an arbitrary quantum channel to an input state. We generalize the concept of a finite-dimensional programmable quantum processor to infinite dimension assuming an energy constraint on the input and output of the target quantum channels. By proving reductions to and from finite-dimensional processors, we obtain upper and lower bounds on the program dimension required to approximately implement energy-limited quantum channels. In particular, we consider the implementation of Gaussian channels. Due to their practical …
Error-disturbance uncertainty relations in a superconducting quantum processor
本文在NISQ超导量子处理器上通过顺序弱测量实验检验误差-扰动不确定性关系，发现Heisenberg EDR被违反而Ozawa和Branciard EDR在整个测量强度范围内均成立，验证了普适EDR在含噪量子处理器中的有效性。
The three-qubit conditional swap gate(Fredkin gate) is a universal gate that can be used to create any logic circuit and has many direct usages. In this paper, we experimentally realized Fredkin gate with only three transition pulses in solution of alanine. It appears that no experimental realization of Fredkin gate with fewer pulses has yet been reported up to now. In addition, the simple structure of our scheme makes it easy to be implemented in experiments.
Processing quantum information using quantum three-level systems or qutrits as the fundamental unit is an alternative to contemporary qubit-based architectures with the potential to provide significant computational advantages. We demonstrate a fully programmable two-qutrit quantum processor by utilizing the third energy eigenstates of two transmons. We develop a parametric coupler to achieve excellent connectivity in the nine-dimensional Hilbert space enabling efficient implementations of two-qutrit gates. We characterize our processor by realizing several algorithms like Deutsch-Jozsa, Berns…
Future quantum computers capable of solving relevant problems will require a large number of qubits that can be operated reliably. However, the requirements of having a large qubit count and operating with high-fidelity are typically conflicting. Spins in semiconductor quantum dots show long-term promise but demonstrations so far use between one and four qubits and typically optimize the fidelity of either single- or two-qubit operations, or initialization and readout. Here we increase the number of qubits and simultaneously achieve respectable fidelities for universal operation, state prepara…
Universal quantum processors in spin systems via robust local pulse sequences
该研究提出一种基于Walsh函数参数化外场局域寻址的协议，可将长程相互作用自旋系统的目标哈密顿量映射为鲁棒脉冲序列，实现通用量子模拟与计算，并通过多类示例完成数值验证。
We simulate the evolution of three-node spin chain on the quantum processor of IBM Quantum Experience using the diagonalization of $XX$-Hamiltonian and representing the evolution operator in terms of CNOT operations and one-qubit rotations. We study the single excitation transfer from the first to the third node and show the significant difference between calculated and theoretical values of state transfer probability. Then we propose a method reducing this difference by applying the two-parameter transformation including the shift and scale of the calculated probabilities. { We demonstrate th…
Fault-Tolerant Code Switching Protocols for Near-Term Quantum Processors
针对二维和三维拓扑色编码均无法单独提供通用量子门集的问题，本研究基于标志量子比特构建了资源优化的确定性与非确定性码切换协议，可在现实条件下容错实现通用门集，推进近期容错量子计算发展。
Quantum critical dynamics and emergent universality in decoherent digital quantum processors
研究退相干如何影响非平衡量子临界动力学，揭示退相干在量子处理器中塑造普遍性行为的作用，通过数值模拟和实验证明退相干对临界行为的重塑。
Universal quantum computing with qubits embedded in trapped-ion qudits
本文提出在囚禁离子量子比特（维度 d=3 至 8）中嵌入量子比特的量子电路编译方法，利用单量子比特操作和 Molmer-Sorensen 门实现单、双及多量子比特门，为扩展量子处理器提供新途径。
A low-loss, 24-mode laser-written universal photonic processor in a glass-based platform
本研究制备了首款飞秒激光直写的24模通用光子处理器，通过悬浮波导与微结构优化实现低损耗、低功耗运行，保真度达99.7%，为量子技术提供可扩展的集成光子平台。
We present a quantum kernel method for high-dimensional data analysis using Google's universal quantum processor, Sycamore. This method is successfully applied to the cosmological benchmark of supernova classification using real spectral features with no dimensionality reduction and without vanishing kernel elements. Instead of using a synthetic dataset of low dimension or pre-processing the data with a classical machine learning algorithm to reduce the data dimension, this experiment demonstrates that machine learning with real, high dimensional data is possible using a quantum processor; but…
We propose two different implementations of an asymmetric two-output probabilistic quantum processor, which can implement a restricted set of one-qubit operations. One of them is constructed by combining asymmetric telecloning with a quantum gate array. We analyze the efficiency of this processor by evaluating the fidelities between the desired operation and the one generated by the processor and show that the two output states are the same as the ones produced by the optimal universal asymmetric Pauli cloning machine. The schemes require only local operations and classical communication, they…
Simulating the topological phases of matter in synthetic quantum simulators is a topic of considerable interest. Given the universality of digital quantum simulators, the prospect of digitally simulating exotic topological phases is greatly enhanced. However, it is still an open question how to realize digital quantum simulation of topological phases of matter. Here, using common single- and two-qubit elementary quantum gates, we propose and demonstrate an approach to design topologically protected quantum circuits on the current generation of noisy quantum processors where spin-orbital coupli…
We describe a method for coupling disjoint quantum bits (qubits) in different local processing nodes of a distributed node quantum information processor. An effective channel for information transfer between nodes is obtained by moving the system into an interaction frame where all pairs of cross-node qubits are effectively coupled via an exchange interaction between actuator elements of each node. All control is achieved via actuator-only modulation, leading to fast implementations of a universal set of internode quantum gates. The method is expected to be nearly independent of actuator decoh…
Architectural scaling tradeoffs in modular 3D bosonic quantum processors
该研究针对模块化三维玻色量子处理器，对比三类架构的缩放权衡，建立系统评估框架，为相关硬件设计提供器件级参数依据。
We consider the entanglement manipulation capabilities of the universal covariant quantum cloner or quantum processor circuit for quantum bits. We investigate its use for cloning a member of a bipartite or a genuine tripartite entangled state of quantum bits. We find that for bipartite pure entangled states a nontrivial behavior of concurrence appears, while for GHZ entangled states a possibility of the partial extraction of bipartite entanglement can be achieved.
It has been experimentally proven that realizing universal quantum gates using higher-radices logic is practically and technologically possible. We developed a Parallel Genetic Algorithm that synthesizes Boolean reversible circuits realized with a variety of quantum gates on qudits with various radices. In order to allow synthesizing circuits of medium sizes in the higher radix quantum space we performed the experiments using a GPU accelerated Genetic Algorithm. Using the accelerated GA we compare heuristic improvements to the mutation process based on cost minimization, on the adaptive cost o…
Machine learning for efficient generation of universal hybrid quantum computing resources
本文通过深度强化学习模拟在测量基量子处理器上生成 squeezed cat 状态，成功率达98%，显著优于其他方法。
Blueprint of a Molecular Spin Quantum Processor
针对通用量子处理器的误差难题，提出由分子纳米磁体qudit和超导谐振腔构成的分子自旋量子处理器蓝图，实现通用门与读出，经模拟验证性能优异，证明分子路线的可行性。
Non-Abelian braiding of Fibonacci anyons with a superconducting processor
本文在超导量子处理器上首次实现了斐波那契弦网模型的非阿贝尔拓扑有序态，演示了具有通用计算能力的斐波那契任意子编织，并通过拓扑纠缠熵和融合规则验证了其非平凡拓扑性质。
Quantum computers have the potential to outperform classical computers in a range of computational tasks, such as prime factorisation and unstructured searching. However, real-world quantum computers are subject to noise. Quantifying noise is of vital importance, since it is often the dominant factor preventing the successful realisation of advanced quantum computations. Here we propose and demonstrate an interleaved randomised benchmarking protocol for measurement-based quantum computers that can be used to estimate the fidelity of any single-qubit measurement-based gate. We tested the protoc…
The light's image is the primary source of information carrier in nature. Indeed, a single photon's image possesses a vast information capacity that can be harnessed for quantum information processing. Our scheme for implementing quantum information processing via universal multiport processors employs a class of quantum Fourier optical systems composed of spatial phase modulators and 4f-processors with phase-only pupils having a characteristic periodicity that reduces the number of optical resources quadratically as compared to other conventional path encoding techniques. In particular, this …
We review a recent theoretical proposal for a universal quantum computing platform based on tunable nonlinear electromechanical nano-oscillators, in which qubits are encoded in the anharmonic vibrational modes of mechanical resonators coupled to a superconducting circuitry. The digital quantum simulation of spin-type model Hamiltonians, such as the Ising model in a transverse field, could be performed with very high fidelities on such a prospective platform. Here we challenge our proposed simulator with the actual IBM-Q quantum processor available on cloud. We show that such state-of-art imple…
We propose a quantum dot architecture for enabling universal quantum information processing. Quantum registers, consisting of arrays of vertically stacked self-assembled semiconductor quantum dots, are connected by chains of in-plane self-assembled dots. We propose an entanglement distributor, a device for producing and distributing maximally entangled qubits on demand, communicated through in-plane dot chains. This enables the transmission of entanglement to spatially separated register stacks, providing a resource for the realisation of a sizeable quantum processor built from coupled registe…
Decoherence-protected entangling gates in a silicon carbide quantum node
本研究在硅碳中实现去相干保护的纠缠门，通过动态去耦与超精细相互作用结合，制备高保真度纠缠态，推动量子节点发展。
Superconducting circuits are at the forefront of quantum computing technology because of the unparalleled combination of good coherence, fast gates and flexibility in design parameters. The majority of experiments demonstrating small quantum algorithms in the superconducting architecture have used transmon qubits and transverse qubit-qubit coupling. However, efficient universal digital computing has remained a challenge due to the fact that majority of the state-of-art architectures rely on nearest-neighbor coupling in one or two dimensions. The limited connectivity and the availability of onl…
Implementation of Leaking Quantum Walks on a Photonic Processor
本文在光子处理器上实现了泄露的量子漫步，通过理论模拟和实验探讨了吸收边界对量子动态的影响，展示了可控损耗对干涉和相干性的修改作用。
Current quantum devices execute specific tasks that are hard for classical computers and have the potential to solve problems such as quantum simulation of material science and chemistry, even without error correction. For practical applications it is highly desirable to reconfigure the connectivity of the device, which for superconducting quantum processors is determined at fabrication. In addition, we require a careful design of control lines and couplings to resonators for measurements. Therefore, it is a cumbersome and slow undertaking to fabricate a new device for each problem we want to …
Universal Logical Quantum Photonic Neural Network Processor via Cavity-Assisted Interactions
本文提出一种基于腔辅助三能级原子相互作用的量子光子神经网络架构，利用光子数选择性相位门构建通用门集，实现多模多光子态制备、玻色子纠错码逻辑操作与纠错电路，为近期集成光子硬件上的容错量子计算铺平道路。
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