Like any other manufactured chip, the wiring connecting the quantum dots is locked into place during the chip’s manufacturing. Since different error correction schemes require different connections between qubits, this forces us to commit to specific error-correction schemes during manufacturing. If a better scheme is developed after the chip is made, it may not be possible to switch to it. Less complex algorithms may benefit from simpler error-correction schemes that require less overhead, but we won’t be able to switch schemes with these chips.
So, quantum dots seem to reflect the trade-offs we face with quantum computing: It’s easy for us to make lots of quantum dots and all the hardware needed to manipulate them, but it’s not possible for them to benefit from the flexibility of other types of qubits.
The whole purpose of this new paper is to show that this is not necessarily true.
moveable point
The new work was done in a collaboration between researchers at Delft University of Technology and the startup QTech. The team created a chip that contained a linear array of quantum dots, and they started with a single electron spin at each end. Then, with appropriate electrical signals, they can transfer the spin to the net dot, gradually bringing them closer together. (And, by slowly we mean a fraction of a second here, but relatively slowly compared to basic switching in electronics.)
Once the electrons got close enough, the spin wavefunctions overlapped, allowing the researchers to place a two-qubit gate on them. These manipulations can be used to entangle two spins and thus are needed to create error-corrected logical qubits; These gates are also required to perform calculations.
The researchers then confirmed that they could move the electrons back to their starting state, after which measurements confirmed that their spins had entangled. And since quantum teleportation also requires a two-qubit gate, they showed that the process could be used for teleportation. Teleportation can increase the mobility provided by moving qubits around, as it can be used to move states around once the qubits are widely separated.
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