Quantum computers may pay a price for keeping time
A quantum computer that runs itself using an internal clock can only compute accurately if that clock is precise, and that precision comes with a thermodynamic cost The post Quantum computers may pay a price for keeping time appeared first on Physics World .
Quantum computers often rely on precise timing signals from classical electronics, lasers or magnetic fields to control the qubits, as opposed to being treated independently in conventional calculations. This reliance introduces an additional energy cost, which a team of Austrian researchers have explored in a new study. They propose the concept of an autonomous quantum processing unit (aQPU), which could operate independently without external control.
The aQPU consists of four components: memory, an instruction register for storing programs, a tick register for counting steps, and an internal quantum clock to drive the process. Just like a mechanical machine that runs autonomously, the aQPU aims to minimize human intervention. The researchers discovered an inevitable trade-off between accuracy and thermodynamics.
Inaccurate clock ticks lead to imperfect application of quantum gates, reducing the computation's fidelity. As the clock becomes more accurate, it produces more thermodynamic entropy, often manifested as increased energy dissipation, particularly as heat. While the study does not suggest a practical quantum computer, it offers physicists a more accurate framework to understand the fundamental energy requirements of quantum computation.
Even when quantum gates are theoretically reversible, achieving sufficient precision in their control may incur thermodynamic costs, challenging the assumption of thermodynamically free operations.
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