Increasing Qubit Control the Bristlecone Way.  
Google has been working on improving Bristlecone’s qubit control.  New circuits have been developed which control its qubits from within the quantum computer’s cooling system.  The number of physical connections between the quantum information processing units has been reduced.  Fewer connections equals less time at room temperature; ergo, less chance of environmental disruption spoiling the qubit’s quantum state.  Loss of the qubit state equates to loss of computational data.

About the Controller.  At the International Solid State Circuits Conference in San Francisco, Google’s AI Quantum team unveiled the cryogenic controller fabricated using CMOS technology and designed in partnership with University of Massachusetts professor Joseph Bardin.

Controller Chip Specifications:

Function:  Provides an instruction set for single-qubit operations

Size: 1-millimeter-by-1.6-millimeter

Operating Temperature:  Between 72 F and and -454.27 F

Power Consumption:  2 milliwatts of power or less

Power Savings from Current Controller:  1,000 times less power consumption

Performance:  “Similar” to the current controller

The new controller has two surmountable drawbacks: (1) it only addresses a single qubit;and, (2) it requires several connections outside the cooling system into a room temperature environment.  Though these issues do exist, the team lead states, overall:

“[I]t’s promising progress in the pursuit of reducing the energy required to control qubits while maintaining the control required to perform “high-quality” qubit operations.”

Reference is found here…