MIT engineers advance toward a fault-tolerant quantum computer

Amazing stuff!

"In the future, quantum computers could rapidly simulate new materials or help scientists develop faster machine-learning models, opening the door to many new possibilities.

But these applications will only be possible if quantum computers can perform operations extremely quickly, so scientists can make measurements and perform corrections before compounding error rates reduce their accuracy and reliability.

The efficiency of this measurement process, known as readout, relies on the strength of the coupling between photons, which are particles of light that carry quantum information, and artificial atoms, units of matter that are often used to store information in a quantum computer.

Now, MIT researchers have demonstrated what they believe is the strongest nonlinear light-matter coupling ever achieved in a quantum system. Their experiment is a step toward realizing quantum operations and readout that could be performed in a few nanoseconds. ..."

From the abstract:

"Light-matter interaction between an atom and an electromagnetic resonator is ubiquitous in quantum technologies. Although linear light-matter coupling 

 can reach the ultrastrong regime g/ω > 10−1, nonlinear light-matter coupling 

 is typically perturbative and limited to χ/ω < 10−2. 

Nonlinear coupling has the advantage of commuting with the atomic  and photonic Hamiltonian, allowing for fundamental operations such as quantum-non-demolition measurement.

Here, we use a superconducting circuit to demonstrate the experimental realization of near-ultrastrong χ/ω = (4.852 ± 0.006) × 10−2. We also show signatures of light-light nonlinear coupling () and χ/2π = 580.3 ± 0.4 MHz matter-matter nonlinear coupling (), representing the largest reported ZZ interaction between two coherent qubits.

Such advances in the nonlinear coupling strength of light, matter modes enable new physical regimes and could lead to orders of magnitude faster qubit readout and gates."

MIT engineers advance toward a fault-tolerant quantum computer | MIT News | Massachusetts Institute of Technology "Researchers achieved a type of coupling between artificial atoms and photons that could enable readout and processing of quantum information in a few nanoseconds."

Near-ultrastrong nonlinear light-matter coupling in superconducting circuits (open access)

Fig. 1: Quarton coupler physics and experimental device.

Fig. 3: Near-ultrastrong nonlinear coupling between linearized transmon A (light) and transmon qubit B (matter).