A blueprint for demonstrating quantum supremacy with superconducting qubits

Neill, C.; Roushan, P.; Kechedzhi, Kostyantyn; Boixo, Sergio; Isakov, Sergei V.; Smelyanskiy, Vadim; Megrant, A.; Chiaro, B.; Dunsworth, A.; Arya, Kunal; Barends, R.; Burkett, Brian; Chen, Y.; Chen, Z.; Fowler, Austin G.; Foxen, Brooks; Giustina, Marissa; Graff, Rob; Jeffrey, E.; Huang, Trent; Kelly, J.; Klimov, Paul V.; Lucero, Erik; Mutus, J.; Neeley, M.; Quintana, Chris; Sank, D.; Vainsencher, A.; Wenner, J.; White, T.; Neven, Hartmut; Martinis, John M.

doi:10.1126/science.aao4309

Cited by 445 publications

(414 citation statements)

References 33 publications

(28 reference statements)

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“…This post-processing is sufficient for the application in this paper (state overlap), although other applications may require a more general form of post-processing. Note that in our approach it is enough to consider measurements in the computational basis, as any change of the measurement basis can be incorporated into the gate sequence in equation (2). In particular, this implies that equation (3) is general enough to cover the expectation values of all Pauli product operators.…”

Section: Algorithmmentioning

confidence: 99%

Learning the quantum algorithm for state overlap

et al. 2018

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Short-depth algorithms are crucial for reducing computational error on near-term quantum computers, for which decoherence and gate infidelity remain important issues. Here we present a machine-learning approach for discovering such algorithms. We apply our method to a ubiquitous primitive: computing the overlap rs ( ) Tr between two quantum states ρ and σ. The standard algorithm for this task, known as the Swap Test, is used in many applications such as quantum support vector machines, and, when specialized to ρ=σ, quantifies the Renyi entanglement. Here, we find algorithms that have shorter depths than the Swap Test, including one that has a constant depth (independent of problem size). Furthermore, we apply our approach to the hardware-specific connectivity and gate sets used by Rigetti's and IBM's quantum computers and demonstrate that the shorter algorithms that we derive significantly reduce the error-compared to the Swap Test-on these computers.

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Section: Algorithmmentioning

confidence: 99%

Learning the quantum algorithm for state overlap

et al. 2018

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“…Universal quantum computing (QC) promises to deliver exponential speed-ups to challenging computational problems-ranging from large integer factorization [1] and solving linear systems of equations [2] to simulation of quantum many-body systems [3][4][5]. Many approaches to quantum computation have been explored in the last two decades, including trapped ions and neutral atoms [6][7][8][9], cavity QED and nonlinear optics [10][11][12], as well as superconducting circuits [13] and spin-based systems [14,15]. Approaches using ultracold polar molecules, in particular, have gained traction in recent years as a potential platform for QC [16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

A scalable quantum computing platform using symmetric-top molecules

et al. 2019

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We propose a new scalable platform for quantum computing (QC)-an array of optically trapped symmetric-top molecules (STMs) of the alkaline earth monomethoxide (MOCH 3 ) family. Individual STMs form qubits, and the system is readily scalable to 100-1000 qubits. STM qubits have desirable features for QC compared to atoms and diatomic molecules. The additional rotational degree of freedom about the symmetric-top axis gives rise to closely spaced opposite parity K-doublets that allow full alignment at low electric fields, and the hyperfine structure naturally provides magnetically insensitive states with switchable electric dipole moments. These features lead to much reduced requirements for electric field control, provide minimal sensitivity to environmental perturbations, and allow for 2-qubit interactions that can be switched on at will. We examine in detail the internal structure of STMs relevant to our proposed platform, taking into account the full effective molecular Hamiltonian including hyperfine interactions, and identify useable STM qubit states. We then examine the effects of the electric dipolar interaction in STMs, which not only guide the design of high-fidelity gates, but also elucidate the nature of dipolar exchange in STMs. Under realistic experimental parameters, we estimate that the proposed QC platform could yield gate errors at the 10 −3 level, approaching that required for fault-tolerant QC.

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“…For the same size of Hilbert space, the number of d-level qudits required is smaller than the number of qubits by the factor d log 2 [16,17], as shown in figure 1. For example, to perform a computation that is beyond the capabilities of any current classical computer (termed quantum supremacy [18]) requires about 50 qubits [19] but only 15 ten-level qudits. Additionally, the time required to carry out gate operations can be reduced by a factor of ( ) d log 2 2 [16,20] if arbitrary transformations can be achieved in the d-dimensional space.…”

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confidence: 99%

Ultracold polar molecules as qudits

et al. 2020

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We discuss how the internal structure of ultracold molecules, trapped in the motional ground state of optical tweezers, can be used to implement qudits. We explore the rotational, fine and hyperfine structure of 40 Ca 19 F and 87 Rb 133 Cs, which are examples of molecules with 2 Σ and 1 Σ electronic ground states, respectively. In each case we identify a subset of levels within a single rotational manifold suitable to implement a four-level qudit. Quantum gates can be implemented using two-photon microwave transitions via levels in a neighboring rotational manifold. We discuss limitations to the usefulness of molecular qudits, arising from off-resonant excitation and decoherence. As an example, we present a protocol for using a molecular qudit of dimension d=4 to perform the Deutsch algorithm.

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A blueprint for demonstrating quantum supremacy with superconducting qubits

Cited by 445 publications

References 33 publications

Learning the quantum algorithm for state overlap

Learning the quantum algorithm for state overlap

A scalable quantum computing platform using symmetric-top molecules

Ultracold polar molecules as qudits

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