Quantum Computing: The Quest for More Qubits

The race to build practical quantum computers has shifted into a new phase. Some of the leading technologies are facing size constraints, while others are rapidly catching up. The two primary methods of building quantum computers include superconducting qubits and trapped-ion qubits. However, the use of single neutral atoms held with laser tweezers has become a competitor, and other techniques at an earlier stage of development could yet catch up.

The Quest for Qubits

Quantum computers promise to solve problems that classical computers cannot by harnessing quantum superposition. In quantum computing, information is stored in qubits that can exist in two simultaneous states. However, maintaining the delicate quantum states for as long as possible is challenging. Despite this, progress in the field has exceeded expectations. In 2019, Google claimed that a machine with 54 superconducting qubits performed the first quantum computation that would have taken impossibly long on a classical computer, which researchers refer to as quantum advantage.

Quality and Quantity

IBM has invested heavily in superconducting qubits and aims to improve both their quality and quantity. The company is expected to unveil its first quantum chip that breaches the 1,000-qubit barrier in the coming months. However, scaling up becomes impractical beyond 1,000 superconducting qubits as each qubit must be individually wired to external circuits. The company plans to take a modular approach, linking multiple chips into one machine starting in 2024. Trapped-ion computers have size constraints as they require a separate laser device to control each ion. IonQ, a start-up company, says its approach allows it to pack multiple rows of ions into a single chip, potentially reaching 1,024 qubits.

Tweezer Tech

The use of neutral atoms held with laser tweezers is a promising new technique. It has been gradually developing for over a decade, but now it's "booming," says Giulia Semeghini, a physicist at Harvard University. The approach encodes qubits in the electronic states of atoms or in the spins of atoms' nuclei. It might soon break the 1,000-qubit barrier as well.

Advances in Quantum Computing Techniques

The race to build practical quantum computers continues, and the field is rapidly evolving. Superconducting qubits and trapped-ion qubits have made the most advanced experiments, but other techniques could soon catch up. IBM is working on improving both the quality and quantity of qubits, while IonQ is working on packing more qubits into a single chip. The use of neutral atoms held with laser tweezers is a promising new technique that could soon break the 1,000-qubit barrier.