Berkeley Lab’s Breakthrough: Programmable Qubits for Scalable Quantum Computers

Researchers at Lawrence Berkeley National Laboratory have developed a new technique that could advance the creation of scalable quantum computers. The team, led by Kaushalya Jhuria and Thomas Schenkel, used a femtosecond laser to create and control qubits, or quantum bits, in silicon with precision. This method could enable the connection of quantum nodes across a network, potentially advancing a quantum internet that could transmit more data than current technologies. The researchers also discovered a new quantum emitter, the Ci center, which could serve as a promising candidate for a spin photon qubit.

Advancements in Quantum Computing: A New Approach to Qubit Fabrication

Researchers at the Lawrence Berkeley National Laboratory (Berkeley Lab) have made a significant breakthrough in the field of quantum computing. They have developed a novel method that could potentially enable the large-scale manufacturing of optical qubits in silicon, a crucial step towards the realization of scalable quantum computers. Quantum computers hold the promise of solving complex problems in various fields such as human health, drug discovery, and artificial intelligence at a speed millions of times faster than some of the world’s fastest supercomputers.

Key Takeaways

• Berkeley Lab researchers have reported a major advancement that could bring us closer to a scalable quantum computer.
• Using a femtosecond laser during experiments which explore the role of hydrogen in qubit formation, the researchers developed a method that programs the formation of telecom-band optical qubits in silicon for large-scale manufacturing.
• The technique could enable scalable quantum computers of the future by building on current silicon-based computing infrastructure.

The Challenge of Connecting Qubits

The key to quantum computing lies in the ability to string together billions of qubits, or quantum bits, with atomic precision. However, this has proven to be a significant challenge for researchers. Traditional methods involve placing an entire silicon wafer in a rapid annealing oven at very high temperatures, which results in the random formation of qubits from defects in silicon’s crystal lattice. Without knowing the exact location of the qubits in a material, creating a quantum computer of connected qubits becomes a difficult task.

A Novel Approach to Qubit Formation

The research team at Berkeley Lab has developed a new approach to overcome this challenge. They have used a femtosecond laser to create and “annihilate” qubits on demand, and with precision, by doping silicon with hydrogen. This method could enable the creation of quantum computers that use programmable optical qubits or “spin-photon qubits” to connect quantum nodes across a remote network. This could also advance a quantum internet that is not only more secure but could also transmit more data than current optical-fiber information technologies.

The Role of Femtosecond Laser and Hydrogen in Qubit Formation

The new method involves using a gas environment to form programmable defects called “color centers” in silicon. These color centers are candidates for special telecommunications qubits or “spin photon qubits.” The method also uses an ultrafast femtosecond laser to anneal silicon with pinpoint precision where those qubits should precisely form. A femtosecond laser delivers very short pulses of energy within a quadrillionth of a second to a focused target the size of a speck of dust.

Discovery of a New Quantum Emitter: The Ci Center

In the course of their research, the team made an unexpected discovery: a quantum emitter called the Ci center. Due to its simple structure, stability at room temperature, and promising spin properties, the Ci center is an interesting spin photon qubit candidate that emits photons in the telecom band. The researchers found that processing silicon with a low femtosecond laser intensity in the presence of hydrogen helped to create the Ci color centers. Further experiments showed that increasing the laser intensity can increase the mobility of hydrogen, which passivates undesirable color centers without damaging the silicon lattice.

The team plans to use the technique to integrate optical qubits in quantum devices such as reflective cavities and waveguides, and to discover new spin photon qubit candidates with properties optimized for selected applications. This breakthrough in the ability to form qubits at programmable locations in a material like silicon that is available at scale is an exciting step towards practical quantum networking and computing.