A Dive into the Thermodynamic Aspects of Quantum Computation

^{Source: QuantumComputingInc} 

^{By Amal Pushp, Affiliate Physicist at the Resonance Science Foundation} 

It is quite conventional that the working of classical computers is affected immensely by heat and one might have come across this situation in their lives when their computer failed to function properly due to excessive heating. 

But what about quantum computers? Do thermodynamical factors influence the workings of a quantum computing device? Well, the answer is yes, quantum computers operate using quantum bits or qubits that essentially are in a superposed state exchanging information in binary code. An interesting fact about qubits is that they not only exchange information using 0 and 1 but also intermediate values between 0 and 1. These qubits are very sensitive, in that excessive heat generation could cause work-related defects which in a sense can cause harm to the device as a whole. Another crucial point is that in order to retrieve significant information from the qubit system, the associated quantum states must be dismantled and this could possibly impact the quantum system heavily in a negative manner as the process would be exothermic. 

In recent work, physicists have investigated the thermodynamic effects caused by superconducting quantum systems [1]. The method involves the employment of a Josephson junction which essentially operates on the Josephson effect, an example of macroscopic quantum phenomena wherein a supercurrent flows between two superconductors placed end-to-end or in close proximity to each other. The principal usability of a Josephson junction is to store quantum information. Using superconductors is a plus because it helps enhance the efficiency of the qubits. 

The researchers employed quantum phase slips (QPS) in combination with the Josephson junction. These phase slips are essentially conceptualized as quantum tunneling of pulse in a direction transverse to the weak part of superconductors. This in turn produces dissipation or heat. 

The use of superconducting qubits is loaded with its own pros and cons. As Wolfgang Belzig, an author of the novel work explains: “One of the greatest advantages of superconducting qubits is that they are so large because this size makes them easy to build and control. On the other hand, this can be a disadvantage if you want to put many qubits on a chip. Developers need to take into account that more heat will be produced as a result and that the system needs to be cooled adequately.” 

The new work opens up a whole new direction of research as previously the principal focus in quantum computing research was on technological enhancement and employing the right combination of materials in producing the required qubits. However, the latest work allows researchers to measure the accurate amount of heat produced by superconducting systems which would hopefully take research in quantum computation and associated fields to the next level. In particular, the current authors of the latest work anticipate exciting futuristic experiments based on their innovation and are hopeful that a coherent manipulation of dissipation in QPS-based circuits would help in overcoming excessive heating in devices and thus scale their performances to greater levels.   

References 

[1] E. Gümüş et al, Calorimetry of a phase slip in a Josephson junction, Nature Physics (2023). DOI: 10.1038/s41567-022-01844-0