In this theme, we aim to achieve "high-temperature" operation of silicon qubits, referred to as “hot silicon qubits” (Fig. 1). This involves operating the qubits around 1 Kelvin (K), equivalent to around -272 degrees Celsius. This is higher than the typical operating temperature of solid-state qubits, which is a few tens of millikelvin (mK). By achieving hot silicon qubits, we can improve the permissible circuit power consumption (heat dissipation) and enable closer placement of cryogenic control circuitry. This contributes to the development of large-scale integrated silicon quantum computers. To achieve high-performance hot silicon qubits, we are exploring the "sweet spot" where quantum coherence time is maximized and comparing electron spin and hole spin systems.

• ①We verify the required characteristics for qubit operation in the developed silicon qubit structures.
• ②We overview the current status and challenges of essential technologies for silicon quantum computers.
• ③We confirm that the increase in noise associated with temperature rise is suppressed in the hole spin system.

①: We tested a part of silicon qubit array for qubit operations (Fig. 2). The qubit device showed the expected change in an energy level with magnetic fields, which will allow us to control its spin operation frequency. We also successfully detected single-electron tunneling events in real-time towards reading the spin state. These advancements bring us closer to realizing silicon qubits.
② : We summarized the current status and challenges in a silicon quantum computing. The summary includes discussions on the “quality” (indivisual qubit performance) and the “quantity” (approaches for large-scale integration). It is published to support researchers from various fields in the development of silicon quantum computers.

③ : We investigated the temperature dependence of charge noise in the hole spin system (Fig. 3). The results reveal low noise levels up to 1 K, demonstrating promising performance at higher temperatures. Additionally, at 300 mK, the noise level was comparable to previous studies on electron spins in quantum dots measured at 50 mK or lower.