Why Do Some Quantum Computers Need a “Chandelier Refrigerator” While Others Can Work at 4 Kelvin?
Difference Refrigerator When people first see a quantum computer, many are surprised by how large it looks. Superconducting quantum computers, in particular, are often associated with the now-famous golden “chandelier” hanging inside a massive cryogenic system. By contrast, trapped-ion quantum computers are often described as systems that cool atoms with lasers. That naturally leads to an interesting question: If trapped-ion quantum computers already use laser cooling, why would some of them also use a 4 Kelvin cryogenic system? And how is that different from the dilution refrigerators used in superconducting quantum computers such as Google’s? The short answer is this: The word “cooling” means different things in different quantum computing platforms. In superconducting quantum computers, extreme cooling is a fundamental requirement for the qubits themselves to function. In trapped-ion quantum computers, laser cooling is used to prepare and control the ions, while low-temperatu...