Debate around what makes a good qubit and how best to manufacture them is a sprawling topic. There are many insistent voices favoring one or another approach. Referencing a paper published today in Nature, Intel has offered a quick take on the promise of silicon spin qubits, one of two approaches to quantum computing that Intel is exploring.
Silicon spin qubits, which leverage the spin of a single electron on a silicon device to perform quantum calculations, offer several advantages over the more familiar superconducting qubit counterparts, contends Intel. They are physically smaller, expected to have longer coherence times, should scale well, and are likely to be able to be fabricated using familiar processes.
“Intel has invented a spin qubit fabrication flow on its 300 mm process technology using isotopically pure wafers sourced specifically for the production of spin-qubit test chips. Fabricated in the same facility as Intel’s advanced transistor technologies, Intel is now testing the initial wafers. Within a couple of months, Intel expects to be producing many wafers per week, each with thousands of small qubit arrays,” according to the Intel news brief posted online today.
The topic isn’t exactly new. Use of quantum dots for qubits has long been studied. The new Nature paper, A programmable two-qubit quantum processor in silicon, demonstrated overcoming some of the cross-talk obstacles presented when using quantum dots.
Abstract excerpt: “[W]e overcome these challenges by using carefully designed control techniques to demonstrate a programmable two-qubit quantum processor in a silicon device that can perform the Deutsch–Josza algorithm and the Grover search algorithm—canonical examples of quantum algorithms that outperform their classical analogues. We characterize the entanglement in our processor by using quantum-state tomography of Bell states, measuring state fidelities of 85–89 per cent and concurrences of 73–82 percent. These results pave the way for larger-scale quantum computers that use spins confined to quantum dots.”
Intel emphasizes silicon spin qubits can operate at higher temperatures than superconducting qubits (1 kelvin as opposed to 20 millikelvin). “This could drastically reduce the complexity of the system required to operate the chips by allowing the integration of control electronics much closer to the processor. Intel and academic research partner QuTech are exploring higher temperature operation of spin qubits with interesting results up to 1K (or 50x warmer) than superconducting qubits. The team is planning to share the results at the American Physical Society (APS) meeting in March.”
A link to a simple but neat video (below) explaining programming on a silicon chip is below.
Link to Nature paper: https://www.nature.com/articles/nature25766
Link to full Intel release: https://newsroom.intel.com/news/intel-sees-promise-silicon-spin-qubits-quantum-computing/