Quantum Computing - A 3 Qubit Entangled State Achieved


In a completely controlled array of spin qubits in silicon, a three-qubit entangled state has been achieved. 

The gadget in a false-colored scanning electron micrograph. The aluminum gates are represented by the purple and green structures. Six RIKEN scientists used the gadget to entangle three silicon-based spin qubits. The RIKEN Center for Emergent Matter Science is responsible for this image.

The number of silicon-based spin qubits that can be entangled has been raised from two to three by an all-RIKEN team, emphasizing the promise of spin qubits for implementing multi-qubit quantum algorithms. 

When it comes to specific kinds of computations, quantum computers have the potential to outperform conventional computers. 

They rely on quantum bits, or qubits, which are the quantum equivalents of the bits used in traditional computers. 

Small blobs of silicon known as silicon quantum dots have many characteristics that make them extremely appealing for realizing qubits, despite being less developed than certain other qubit technologies. 

Long coherence periods, high-fidelity electrical control, high-temperature functioning, and a large scaling potential are among them. 

To link multiple silicon-based spin qubits, however, scientists must be able to entangle more than two qubits, a feat that has eluded them until now. 

Seigo Tarucha and five colleagues from RIKEN's Center for Emergent Matter Science have successfully started and measured a three-qubit array on silicon (the probability that a qubit is in the expected state). 

They also used a single chip to integrate the three entangled qubits. 

This demonstration is a first step in expanding the possibilities of spin qubit-based quantum systems. 

"Two-qubit operations are sufficient for performing basic logical computations," Tarucha says. 

"However, for scaling up and incorporating error correction, a three-qubit system is the bare minimum." The team's gadget is controlled by aluminum gates and consists of a triple quantum dot on a silicon/silicon–germanium heterostructure. 

One electron may be found in each quantum dot, and its spin-up and spin-down states encode a qubit. 

An on-chip magnet creates a magnetic-field gradient that divides the three qubits' resonance frequencies, allowing them to be addressed separately. 

The researchers used a two-qubit gate, a tiny quantum circuit that is the building block of quantum computing systems, to entangle two of the qubits. 

By integrating the third qubit with the gate, they were able to achieve three-qubit entanglement. 

The resultant three-qubit state had an astonishing 88 percent state fidelity and was in an entangled state that might be utilized for error correction. 

This demonstration is only the start of an ambitious research program aimed at developing a large-scale quantum computer. 

"With the three-qubit gadget, we aim to show basic error correction and build devices with 10 or more qubits," Tarucha adds. 

"We aim to create 50 to 100 qubits and more advanced error-correction procedures in the next decade, opening the path for a large-scale quantum computer."

~ Jai Krishna Ponnappan

You may also want to read more about Quantum Computing here.

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