Trapped Ion, Superconducting, and Photonic, Oh My!
As we head into last quarter of 2020, we find ourselves in the middle of historic fires in California, a volatile stock market, and a global pandemic. And yet, quantum computing cares not about our social ills. For the quantum computer, this is the era of Noisy Intermediate-Scale Quantum (NISQ) devices. Quantum annealers, though more mature in their development lifecycle are largely limited to optimization problems and thus will not be included in this discussion of quantum tech (for more information on quantum annealers, check out this resource from D-Wave). During this time, two main technologies are currently dominating programmable quantum computing: Superconducting Qubits and Ion Traps.
Superconducting Qubits are favored by the likes of IBM, Google, Rigetti, and Intel just to name a few. Of course, Google’s quantum supremacy seminal experiment was performed on a superconducting device with 53 fully controllable qubits. This technology relies upon a two-level energy system to form a relatively noise-resistant qubit, or at least, one that allows for a demonstration of quantum supremacy. As noted in the helpful infographic from BCG, superconducting qubits are the closest to being a commercially viable quantum device with very fast gating and high fidelity, but suffer from rather mediocre qubit lifetime and limited nearest-neighbor connectivity.
Ion Traps are somewhat less ready for prime time, but are advancing quickly. Companies backing this type of quantum device are IonQ, Honeywell and others. Ion traps utilize single ions that are trapped in magnetic fields, where the spin of the atom forms the qubit. Honeywell recently announced the launch of the world’s most powerful quantum computer with a quantum volume of 64 using this technology (though IBM now claims that they have achieved the same volume with one of their computers). Trapped ion qubits are relatively stable and benefit from uniform and universal connectivity, long lifetimes and the most robust gate fidelity, but suffer from slow gate operation speeds and current scaling issues.
Three other qubit types are highlighted in this infographic as possible next-generation quantum computing technologies: photonic, silicon-based and topological. These remain as highly active areas of research and development in academia and beyond. Using silicon-based qubits a recent study from researchers at the University of Chicago found that they were able to increase their qubit coherence time by an impressive 10,000 fold. Further advancements in all of these technologies will pave the way for computing beyond the NISQ era and into the age of fault-tolerant quantum computing.