Implementation of XY entangling gates with a single calibrated pulse

Abrams, Deanna; Didier, Nicolas; Johnson, Blake; Silva, Marcus; Ryan, Colm A.

doi:10.1038/s41928-020-00498-1

Cited by 94 publications

(64 citation statements)

References 43 publications

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“…Approaches such as the QAOA, as implemented in Refs. [1,5,21,36,37,41,49], fall into the first category and benefit from being able to exploit some extent of adiabatic computing to search the Hilbert space [2]. In principle, the produced variational state is guaranteed to converge towards the exact solution for infinitely long quantum evolution U cp ( θ).…”

Section: Qubo Model and The Complete Encoding Schemementioning

confidence: 99%

“…3, we show the average optimized cost function as a function of circuit depth for 3 QUBO instances of different sizes, n c = 8, 32 and 64, using n q = 4, 6 and 7 qubits respectively 1 . In each instance, 1 We note that the expressive power of |ψ 1 ( θ) can be fully captured within the complete encoding scheme by using only a single layer of Ry(θ i ) rotations applied to each qubit. Studying the minimal encoding scheme is therefore akin to examining the amount of resources required to map the simplest quantum the elements of A were randomly drawn from a uniform distribution ranging from -1 to 1.…”

Section: Variational Protocol To Solve Randomly Generated Qubo Modelsmentioning

confidence: 99%

“…The set of numbers displayed next to the edges between the vertices labeled xi and xj represents the probabilitiesP i,j = (P i,j 0,0 ,P i,j 1,0 ,P i,j 0,1 ,P i,j 1,1 ) with the convention i < j. In this example, assuming thatP 1,2 1,1 = 0.9 has the largest probability in the entire graph, (x1, x2) would be the first pair to be selected in step (1). The remaining steps are outlined in the main text.…”

Section: Averaging the Probabilities And Defining The Cost Functionmentioning

confidence: 99%

“…In this section, we compared the minimal encoding approach to the Quantum Approximate Optimization Algorithm (QAOA) under the effects of noise. QAOA is a commonly employed technique used to solve binary optimization problems on NISQ devices [1,5,13,21,36,37,41,49,51], where each classical variable is represented by a single qubit (complete…”

Section: Comparison With Qaoamentioning

confidence: 99%

“…In addition to increasing algorithmic difficulties, the engineering overhead of scaling up the quantum hardware also currently limits the size of computational tasks to toy models. Previously proposed schemes to implement quantum algorithms to solve optimization problems have used a number of classical variables equal to the number of qubits available and were therefore limited to problem sizes involving only a few tens of them [1,5,6,21,36,37,41,42,49]. This is not representative of real-world optimization problems, where the number of classical variables n c involved can be on the order of 10 4 .…”

Section: Introductionmentioning

confidence: 99%

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Qubit-efficient encoding schemes for binary optimisation problems

Tan

Lemonde

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et al. 2021

Quantum

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We propose and analyze a set of variational quantum algorithms for solving quadratic unconstrained binary optimization problems where a problem consisting of nc classical variables can be implemented on O(log⁡nc) number of qubits. The underlying encoding scheme allows for a systematic increase in correlations among the classical variables captured by a variational quantum state by progressively increasing the number of qubits involved. We first examine the simplest limit where all correlations are neglected, i.e. when the quantum state can only describe statistically independent classical variables. We apply this minimal encoding to find approximate solutions of a general problem instance comprised of 64 classical variables using 7 qubits. Next, we show how two-body correlations between the classical variables can be incorporated in the variational quantum state and how it can improve the quality of the approximate solutions. We give an example by solving a 42-variable Max-Cut problem using only 8 qubits where we exploit the specific topology of the problem. We analyze whether these cases can be optimized efficiently given the limited resources available in state-of-the-art quantum platforms. Lastly, we present the general framework for extending the expressibility of the probability distribution to any multi-body correlations.

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Section: Qubo Model and The Complete Encoding Schemementioning

confidence: 99%

Section: Variational Protocol To Solve Randomly Generated Qubo Modelsmentioning

confidence: 99%

Section: Averaging the Probabilities And Defining The Cost Functionmentioning

confidence: 99%

Section: Comparison With Qaoamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Qubit-efficient encoding schemes for binary optimisation problems

Tan

Lemonde

Thanasilp

et al. 2021

Quantum

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Generation of Perfectly Entangled Two and Three Qubits States by Classical Random Interaction

Akram

2022

Annalen der Physik

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This study examines the possibility of finding perfect entanglers for a Hamiltonian which corresponds to several quantum information platforms of interest at the present time. However, in this study, a superconducting circuit is used that stands out from other quantum‐computing devices, especially because transmon qubits can be coupled via capacitors or microwave cavities, which enables to combine high coherence, fast gates, and high flexibility in its design parameters. There are currently two factors limiting the performance of superconducting processors: timing mismatch and the limitation of entangling gates to two qubits. In this work, a two‐qubit SWAP and a three‐qubit Fredkin gate is presented, additionally, a perfect adiabatic entanglement generation between two and three programmable superconducting qubits is also demonstrated. Furthermore, the impact of random dephasing, emission, and absorption noises on the quantum gates and entanglement is also demonstrated in this study. It is demonstrated by numerical simulation that CSWAP gate and W‐state generation can be achieved perfectly in one step with high reliability under weak coupling conditions. Hence, this scheme could contribute to quantum teleportation, quantum communication, and some other areas of quantum information processing.

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Phase Calibration of the Parametric Gate in the Superconducting Circuits

Liu

Guan

Liu

et al. 2022

Physica Status Solidi (b)

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The quantum gate, as the foundation of quantum computation, depends on the architecture of the quantum chip, especially in superconducting systems. The parametric modulation to the flux bias is an important protocol to realize the multi‐qubit gate, which has some intrinsic advantages. Similar to other two‐qubit operations, parametric gates leave the extra phase in single‐qubit space, which is required to be corrected. In this article, the relation between the phases of the modulated pulse and the applied microwaves is experimentally characterized. By adjusting the envelope shape and phase of the applied pulses, the extra phase of the one qubit generated by the two‐qubit gate is suppressed via a simple and fast Ramsey‐like experiment. The tomography results demonstrate that this protocol is an effective calibrating method for future large‐scale quantum circuit manipulation.

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Implementation of XY entangling gates with a single calibrated pulse

Cited by 94 publications

References 43 publications

Qubit-efficient encoding schemes for binary optimisation problems

Qubit-efficient encoding schemes for binary optimisation problems

Generation of Perfectly Entangled Two and Three Qubits States by Classical Random Interaction

Phase Calibration of the Parametric Gate in the Superconducting Circuits

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