The Grand Staircase of Quantum Computing

Ironically, it's deterministic.

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The Quantum Dragon finally got around to seeing the Harry Potter movies, and he is thoroughly fascinated by the magically whimsical Grand Staircase inside Hogwarts Castle: 142 staircases that constantly move, changing which corridors connect to which, and opening up new routes while simultaneously creating barriers for others. He’s not magical, so you can see him above trying to figure out how to mimic the effect. Unfortunately, limestone staircases are relatively heavy to fly around, so maybe he can steal some ideas from Quantum Art.

Dynamically Reconfigurable Optical Segmentation

Quantum Art takes very long ion chains and uses optical tweezers, similar to those used in neutral atom quantum computers, to create barriers of ions. The tweezers don’t trap the ions, because the ions are already trapped. Instead, they create segments of ions, or registers, within the chain. Each segment is a core with all-to-all connectivity. Each core can implement native multi-qubit gates to mitigate error propagation. The cores are dynamically reconfigured optically, which is more akin to sliding doors open and closed, instead of in space, like shuttling, which is more akin to waiting for a staircase to slowly move across a chasm.

• No photonic interconnects, which can be probabilistic like the Grand Staircase

• No mechanical shuttling, which is quite slow and is only 1-to-1

• No carrying heavy limestone across a grand cavern

1,000,000 Qubits

The genesis of this article was actually me challenging Quantum Art’s roadmap to 1,000,000 qubits. Almost everyone has one these days, and they’re quite frankly not believable. So, we had a call, and the premise was simple: make me a believer. And then the description of the technology led to the staircase analogy.

Anyway, the key to the claim seems to be 1,000,000 ions in a single vacuum chamber. Depending on who you ask, neutral atoms scale to 10s of 1000s in a single vacuum chamber, up to 100,000 atoms, so 1,000,000 ions in a vacuum chamber is an extension of that premise. The approach avoids the constraints of dilution refrigerators and the need to interconnect them, so the challenge is controlling that many ions/atoms in one vacuum chamber.

2.5 Challenges

Speaking of challenges, there are some. The company identifies 2.5 of them, to be precise:

• 0.5 (traps) — We need trapping technology that can allow large numbers of stable qubits to be held; a 200-ion chain is believed to be a record

• 1.0 (hardware) — The optical delivery system, with 1 laser per qubit, is an engineering and control challenge; a solution might be able to borrow from lithography with its nanometer precision (instead of micron precision)

• 1.0 (software) — More ions create more degrees of freedom; Quantum Art has published 3 papers on its compiler

Epilogue

If you had to physically carry limestone staircases around, you too would quickly look for alternatives. The Quantum Dragon is now investigating optical tweezers as a solution, while I beg and plead with him that his cave doesn’t need 1,000,000 stairs, let alone staircases.

While this article was awaiting publication, Quantum Art announced it has raised $100M in a Series A round to support scaling to 1,000 qubits.

Filed under: Quantum Computing • Hardware Innovation • Emerging Technologies

1. Image generated by an AI model provided by Microsoft Copilot and Google’s language model AI.