Co-designing a scalable quantum computer with trapped atomic ions

Abstract

The first generation of quantum computers are on the horizon, fabricated from quantum hardware platforms that may soon be able to tackle certain tasks that cannot be performed or modelled with conventional computers. These quantum devices will not likely be universal or fully programmable, but special-purpose processors whose hardware will be tightly co-designed with particular target applications. Trapped atomic ions are a leading platform for first-generation quantum computers, but they are also fundamentally scalable to more powerful general purpose devices in future generations. This is because trapped ion qubits are atomic clock standards that can be made identical to a part in 10 15 , and their quantum circuit connectivity can be reconfigured through the use of external fields, without modifying the arrangement or architecture of the qubits themselves. In this forwardlooking overview, we show how a modular quantum computer with thousands or more qubits can be engineered from ion crystals, and how the linkage between ion trap qubits might be tailored to a variety of applications and quantum-computing protocols. Quantum information processors have the potential to perform computational tasks that are difficult or impossible using conventional modes of computing. 1-3 In a radical departure from classical information, the qubits of a quantum computer can simultaneously store bit values 0 and 1, and when measured they probabilistically assume definite states. Many interacting qubits, isolated from their environment, can represent huge amounts of information: there are exponentially many binary numbers that can co-exist, with entangled qubit correlations that can behave as invisible wires between the qubits. Even in the face of Moore's Law, or the doubling in conventional computer power every year or two, the complexity of massively entangled quantum states of just a few hundred qubits can easily eclipse the capacity of classical information processing. 4 There are but a few known applications that exploit this quantum advantage, such as Shor's factoring algorithm, 5 and future quantum information processors will likely be applied to special-purpose applications. On the other hand, a quantum computer has not yet been built; therefore, new quantum applications and algorithms will likely follow from the evolution and capability of quantum hardware.In the 20 years since the advent of Shor's algorithm 5 and the discovery of quantum error correction, 6-8 there has been remarkable progress in demonstrations of entangling quantum gates on o10 qubits in certain physical systems. Current efforts aim to scale to hundreds, thousands or even millions of interacting qubits. Unlike the classical scaling of bits and logic gates, however, large quantum systems are not comparable to the behaviour of just a few qubits. Just because 2 or 4 qubits can be completely controlled with negligible errors does not mean that this system can readily scale to 4100 qubits.In the last few years, two particular quantum hardware platforms have e...

Sympathetic cooling of protons and antiprotons with a common endcap Penning trap

“…Doppler cooled ions, for example, at sub mK temperatures, are the foundation of successful trapped ion quantum information experiments (25)(26)(27). Likewise ions in rf traps (28), and more recently Penning traps (29), are routinely prepared in the ground state.…”

Performing quantum computing experiments in the cloud

“…The first experiment implemented on the IBM chip is a basic Rabi oscillation spectra across a logically encoded qubit using a distance two surface code. Surface code quantum computing [4], is now the standard model used for large-scale quantum computing development [8][9][10][11][12][13][14][15][16][17][18] and results from superconducting and other technologies show extraordinary promise [19][20][21][22][23]. While the distance three, 5-qubit code [24] could be used with the IBM QE, we focus on the surface code due to its relevance to larger quantum architectures.…”

Simulating the performance of a distance-3 surface code in a linear ion trap

“…The underlying connection graph of a trapped linear ion chain is a fully connected graph [105]. Therefore, there are many ways to map the surface-17 code to the linear ion chain.…”