Most researchers agree that many challenges remain in the quest to build a practical quantum computer. In a paper published in Nature, Chow's team described its progress in tackling one of those challenges, by designing a way to detect errors on a two-by-two lattice of superconducting quantum bits.
If there are errors in the underlying data stored by any computer then the results of its calculations will be incorrect. Errors rarely occur in the transistors used to build classical computers, and when they do, they are automatically fixed by various error-correction schemes.
Quantum computers are a different story. "Qubits are really susceptible to errors," says Chow. "They can be affected by heat. They can be affected by noise in the environment. They can be affected by stray electromagnetic couplings."
Only one type of error can occur in the information stored by a classical computer, a bit-flip, where a 0 is mistakenly flipped to 1 or vice versa. Qubits suffer from bit-flits but also from phase errors. A superposition state of a qubit, or having the values 0 and 1 at the same time, is denoted as "0+1". A phase error flips the sign of the phase relationship between 0 and 1.
"0+1 and 0-1 are very different in terms of the information that’s in that state," explains Chow. "We have to think of it as an arrow pointing along a sphere. You can point at the south pole and that’s a zero. You can also be pointing at the north pole and that’s a one. You can point along the equator and that’s a 0+1 but if you point to the exact opposite side of that equator, it’s a 0-1." To make things even more complicated, quantum error correction schemes have to avoid measuring qubit data directly since that will cause the value to collapse.
IBM’s new error-detection scheme is based on a technique called surface code which spreads quantum information across many qubits. Two syndrome (or measurement) qubits are coupled with two code, or data qubits. One syndrome qubit reveals whether a bit-flip error has occurred to either of the code qubits, while the other syndrome qubit flags the case where a phase-flip error occurred, all without directly measuring either of the qubits.
But error correction is just one of the obstacles on the rocky road to building a practical quantum computer.
One professor posted a lengthy list of those obstacles on Quora.
- The Golden Age Of Quantum Computing Is Upon Us (Once We Solve These Tiny Problems)
If there are errors in the underlying data stored by any computer then the results of its calculations will be incorrect. Errors rarely occur in the transistors used to build classical computers, and when they do, they are automatically fixed by various error-correction schemes.
Quantum computers are a different story. "Qubits are really susceptible to errors," says Chow. "They can be affected by heat. They can be affected by noise in the environment. They can be affected by stray electromagnetic couplings."
Only one type of error can occur in the information stored by a classical computer, a bit-flip, where a 0 is mistakenly flipped to 1 or vice versa. Qubits suffer from bit-flits but also from phase errors. A superposition state of a qubit, or having the values 0 and 1 at the same time, is denoted as "0+1". A phase error flips the sign of the phase relationship between 0 and 1.
"0+1 and 0-1 are very different in terms of the information that’s in that state," explains Chow. "We have to think of it as an arrow pointing along a sphere. You can point at the south pole and that’s a zero. You can also be pointing at the north pole and that’s a one. You can point along the equator and that’s a 0+1 but if you point to the exact opposite side of that equator, it’s a 0-1." To make things even more complicated, quantum error correction schemes have to avoid measuring qubit data directly since that will cause the value to collapse.
IBM’s new error-detection scheme is based on a technique called surface code which spreads quantum information across many qubits. Two syndrome (or measurement) qubits are coupled with two code, or data qubits. One syndrome qubit reveals whether a bit-flip error has occurred to either of the code qubits, while the other syndrome qubit flags the case where a phase-flip error occurred, all without directly measuring either of the qubits.
But error correction is just one of the obstacles on the rocky road to building a practical quantum computer.
One professor posted a lengthy list of those obstacles on Quora.
- The Golden Age Of Quantum Computing Is Upon Us (Once We Solve These Tiny Problems)
No comments:
Post a Comment