Summary:
Researchers at Purdue, Delft and Melbourne have created a new, hybrid molecule in which its quantum state can be intentionally manipulated, a required step in the building of quantum computers. The device consists of a single donor atom (arsenic) in a gated nanostructure. By controlling the voltage, the researchers found that they could make an electron go to either end of the molecule or exist in an intermediate, quantum, state. Measurements on the device could only be interpreted by considering the dopant to be made of two parts. One end comprised the arsenic atom embedded in the silicon, while the 'artificial' end of the molecule forms near the silicon surface of the transistor. A single electron was spread across both ends. (Published: 27/06/08)
Notes:
- Gerhard Klimeck, prof. electrical and computer engineering at Purdue Univ.
- "Up to now large-scale quantum computing has been a dream. This development may not bring us a quantum computer 10 years faster, but our dreams about these machines are now more realistic."
- Quantum computers
- would harness the strange behaviors found in quantum physics to create computers that would carry information using quantum bits, or qubits.
- would be able to process exponentially more information
- If a traditional computer were given the task of looking up a person's phone number in a telephone book, it would look at each name in order until it found the right number.
- A quantum computer could look at all of the names in the telephone book simultaneously.
- could take advantage of the bizarre behaviors of quantum mechanics in ways that are hard to fathom
- e.g. two quantum computers could, in concept, communicate instantaneously across any distance imaginable, even across solar systems
- challenge until now had been to create a computer semiconductor in which the quantum state could be controlled, creating a qubit.
- Klimeck: "If you want to build a quantum computer you have to be able to control the occupancy of the quantum states. We can control the location of the electron in this artificial atom and, therefore, control the quantum state with an externally applied electrical field."
- single donor atom in a gated nanostructure
- observed evidence for a new hybrid molecule in the solid-state
- Hollenberg: "Measurements only made sense if the molecule was considered to be made of two parts. One end comprised the arsenic atom embedded in the silicon, while the 'artificial' end of the molecule forms near the silicon surface of the transistor. A single electron was spread across both ends."
- "What is strange about the 'surface' end of the molecule is that it occurs as an artifact when we apply electrical current across the transistor and hence can be considered 'manmade.' We have no equivalent form existing naturally in the world around us."
- By controlling the voltage, the researchers found that they could make an electron go to either end of the molecule or exist in an intermediate, quantum, state.
- Sven Rogge, Delft Univ. of Technology:
- "Our experiment made us realize that industrial electronic devices have now reached the level where we can study and manipulate the state of a single atom. This is the ultimate limit, you can not get smaller than that."
