&Bullet; physics 14, s59

The researchers suppress measurement fluctuations of microwaves in a cavity down to below the vacuum.

R. Dassonneville et al.[1]

For most quantum physics applications, dissipative interactions – those that occur between a quantum system and its environment – are the enemy, as they can ruin delicate and carefully prepared quantum states. Benjamin Huard of the École Normale Supérieure in Lyon, France, and colleagues have now used the phenomenon to their advantage and, using the “dissipation technique”, “squeezed” microwave light in a cavity to an unprecedented level. The technology could enable qubits to be read out more quickly in a superconducting quantum computer and ultimately enable the sharing of entangled states across quantum networks.

Quantum fluctuations limit how precisely researchers can measure certain pairs of properties of a light wave, such as: B. the amplitude and phase of their electric field. The uncertainty in one property can be reduced to levels below that of quantum fluctuations at the expense of greater uncertainty in the other property, a process known as quantum squeezing. For the propagation of light waves, there is no limit to this uncertainty reduction, but for light in a cavity the reduction has a threshold value known as the 3 dB limit.

Huard and his colleagues show that they can cross this limit by “squeezing out” the light before it enters the cavity. To do this, the team coupled its cavity to a second, highly dissipative “dump” cavity using a non-linear device called a Josephson Ring Modulator (JRM). Pumping the JRM with two microwave tones at different frequencies created an exchange between the two cavities, causing the dump cavity to introduce already compressed light into the cavity of interest. The roughly 8 dB squeeze they achieved with this procedure is a record for a microwave cavity.

–Marric Stephens

Marric Stephens is Corresponding Editor for physics based in Bristol, UK.


  1. R. Dassonneville et al., “Dissipative stabilization of squeezing above 3 dB in microwave mode” PRX Quantum2020323 (2021).

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