Superconducting Qubit (Transmon)
A tiny superconducting circuit can act as a quantum bit: shown in 1999, and made stable enough by the 2007 transmon design to be the building block of Google's and IBM's quantum chips.
Open in the interactive tree →In 1999 Nakamura, Pashkin and Tsai showed that a tiny superconducting island (a single-Cooper-pair box) can be put into a controlled quantum superposition, the first superconducting qubit; at first the state lasted less than a nanosecond. In 2007 a team at Yale and Sherbrooke introduced the transmon, a design far less sensitive to electrical noise, and coherence times have since grown by roughly five orders of magnitude. Transmons are the qubits of Google's 105-qubit Willow chip and of IBM's processors, so today's superconducting quantum computers all rest on this step.
Prerequisites
- Cryogenics (Liquefied Air & Helium)1895-1908Qubits only work in refrigerators cooled to a few thousandths of a degree above zero.
- Superconductivity1911Resistance-free metal keeps the fragile quantum state from leaking away.
- Josephson Effect & SQUIDs1962-1964The qubit's two states come from a Josephson junction in the circuit.
- Quantum Computing Concept1981-1985It is a real device for the two-state quantum bit the idea needs.
Unlocks
- First Quantum Processors2019Google's and IBM's quantum processors are arrays of transmon qubits.