Abstract
To achieve scalable quantum computing, improving entangling-gate fidelity and its implementation efficiency are of utmost importance. We present here a linear method to construct provably power-optimal entangling gates on an arbitrary pair of qubits on a trapped-ion quantum computer. This method leverages simultaneous modulation of amplitude, frequency, and phase of the beams that illuminate the ions and, unlike the state of the art, does not require any search in the parameter space. The linear method is extensible, enabling stabilization against external parameter fluctuations to an arbitrary order at a cost linear in the order. We implement and demonstrate the power-optimal, stabilized gate on a trapped-ion quantum computer.
Highlights
Representing and processing information according to the laws of quantum physics, a quantum computer may surpass the computational power of a classical computer by many orders of magnitude and is expected to transform areas such as machine learning[1,2], cryptosystems[3], materials science[4,5], and finance[6,7], to name only a few
Highlighting the importance of efficient and robust implementation of XX gates, Fig. 1 shows the resource requirements for various quantum computations. For this figure and for near-term, pre- faulttolerant (FT) quantum computers, we considered variational quantum eigensolvers that compute the ground state of the water molecule[19], a material spin-dynamics undergoing state-evolution according to the Heisenberg Hamiltonian[5], a quantum approximate optimization algorithm addressing a maximum-cut problem relevant for various optimization problems[20], the widely-employed quantum Fourier transform subroutine[21], quantum factoring of a 1024-bit integer[22], which is meaningful for cybersecurity, and data-driven quantum-circuit learning for certain visual patterns[2]
Because, e.g., the Fourier basis is complete in its respective symmetry class, the resulting g(t) is provably optimal in regime, the resource cost is measured in T gates, where each FT T gate requires tens of hardware-implementation-level XX gates[26,27]
Summary
Representing and processing information according to the laws of quantum physics, a quantum computer may surpass the computational power of a classical computer by many orders of magnitude and is expected to transform areas such as machine learning[1,2], cryptosystems[3], materials science[4,5], and finance[6,7], to name only a few. The trapped-ion quantum information processor (TIQIP) is one of the most promising architectures for achieving a universal, programmable quantum computer, operating according to the gate model of quantum computing. Apart from a set of singlequbit gates, only a single entangling, two-qubit gate is necessary for achieving this goal. A host of pulse-shaping techniques have been devised[9,12,13,17,18] to better control the underlying trappedion quantum systems for more efficient XX gate implementation, while reducing errors
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