4 ms·

Artificial atoms create stable qubits for quantum computing

71 points by dnetesn 7y ago

ganzuul 7y ago
> Abstract > Once the periodic properties of elements were unveiled, chemical behaviour could be understood in terms of the valence of atoms. Ideally, this rationale would extend to quantum dots, and quantum computation could be performed by merely controlling the outer-shell electrons of dot-based qubits. Imperfections in semiconductor materials disrupt this analogy, so real devices seldom display a systematic many-electron arrangement. We demonstrate here an electrostatically confined quantum dot that reveals a well defined shell structure. We observe four shells (31 electrons) with multiplicities given by spin and valley degrees of freedom. Various fillings containing a single valence electron—namely 1, 5, 13 and 25 electrons—are found to be potential qubits. An integrated micromagnet allows us to perform electrically-driven spin resonance (EDSR), leading to faster Rabi rotations and higher fidelity single qubit gates at higher shell states. We investigate the impact of orbital excitations on single qubits as a function of the dot deformation and exploit it for faster qubit control.
pauljurczak 7y ago
Nice work, but "infinitesimally small space of only around 10 nanometres in diameter" really rubs me the wrong way. Well, at least they are not using diameter of human hair as a unit of measure.
- numlock86 7y ago
  > Well, at least they are not using diameter of human hair as a unit of measure. I recently heard a scientific talk mentioning that the earth is losing around three slices of mortadella in helium every second ...
  - pr_nik 7y ago
    In defense of academics resorting to such comparisons, making this tangible, exciting, accessible, and generally common sense-compatible is all the rage nowadays. The attention economy certainly rules the PR-side of academia and success there can translate into cash for basic research. Not my idea, not my style, but it's a thing.
    - Koshkin 7y ago
      Problem is, those who might need this sort of comparisons never read such articles. (Educated people already know what a nanometer is.)
  - Iwan-Zotow 7y ago
    HOw many olympic size pools? Or football fields?
Animats 7y ago
This is either Nobel Prize material or total bullshit. Which is it? This could be a huge breakthrough in quantum computing. Or it could just be a capacitor with delusions of grandeur. Don't know.
- jeeceebees 7y ago
  Have all novel qubits gotten nobel prizes so far? I think there's more than enough room in between bullshit and nobel prize. This looks very promising, but as always the devil is in the details. The next steps are multiqubit gates, then linking those up into useful quantum circuits, and then hopefully doing actual quantum computations. Personally I wouldn't expect a nobel prize until one of those last 2 steps. There's a lot of hurdles before then to run into some nasty problems.
- google234123 7y ago
  Since they could only publish in Nature Communications it's probably BS.
  - selimthegrim 7y ago
    See my comment above.
- peacockwank 7y ago
  lol, nah. I did my own PhD thesis a couple years ago on donor atoms in silicon, specifically selenium, forming hydrogen and helium like systems that "could" have been useful for forming a qbit. tldr selenium has 2 more valence electrons than silicon so when it is substitutionally doped into silicon then you get a helium like system, which in some cases ends up hydrogen like when, presumably, imperfections either local or remote cause enough disruption to whisk away/capture one of the electrons, thus forming a hydrogen like system. I didn't investigate the cause of the different molecular like complexes that spring up when you dope silicon like this though, I only probed things with light and did calculations relating to that probing, I didn't do any modelling concerning the diffusion and behaviour of dopants which I kinda regret. Then you can optically manipulate that remaining donor electron. It didn't really work cause it's hard and the lifetimes of the donor electron systems are not great (tens of ns to ~100ns for some of the systems). It was then I realised that physics research is a dangerous thing to attempt if you can't stomach the constant uncertainty and risk about your own personal future, when you are found to be not good enough due to not publishing, so I abandoned academia so I could massively reduce that stress and constant anxiety and actually have a life. So the tldr is that this is not bullshit at all, it is in-fact very interesting and a promising line of work. But it's not going to make anyone's career by itself, and without appropriate pumping of the importance of the work and sufficient mentoring no-one who works on it as a grad student has a future as a researcher. So no, it's neither Nobel Prize material or total bullshit.
the_dege 7y ago
I wasn't able to find it referenced in the article and on the paper, is it at room temperature or still near 0 °Kelvin?
- tagrun 7y ago
  The electron temperature should be around ~100mK

71 points by dnetesn 7y ago

> Abstract > Once the periodic properties of elements were unveiled, chemical behaviour could be understood in terms of the valence of atoms. Ideally, this rationale would extend to quantum dots, and quantum computation could be performed by merely controlling the outer-shell electrons of dot-based qubits. Imperfections in semiconductor materials disrupt this analogy, so real devices seldom display a systematic many-electron arrangement. We demonstrate here an electrostatically confined quantum dot that reveals a well defined shell structure. We observe four shells (31 electrons) with multiplicities given by spin and valley degrees of freedom. Various fillings containing a single valence electron—namely 1, 5, 13 and 25 electrons—are found to be potential qubits. An integrated micromagnet allows us to perform electrically-driven spin resonance (EDSR), leading to faster Rabi rotations and higher fidelity single qubit gates at higher shell states. We investigate the impact of orbital excitations on single qubits as a function of the dot deformation and exploit it for faster qubit control.

pauljurczak 7y ago

Nice work, but "infinitesimally small space of only around 10 nanometres in diameter" really rubs me the wrong way. Well, at least they are not using diameter of human hair as a unit of measure.

numlock86 7y ago
> Well, at least they are not using diameter of human hair as a unit of measure. I recently heard a scientific talk mentioning that the earth is losing around three slices of mortadella in helium every second ...
- pr_nik 7y ago
  In defense of academics resorting to such comparisons, making this tangible, exciting, accessible, and generally common sense-compatible is all the rage nowadays. The attention economy certainly rules the PR-side of academia and success there can translate into cash for basic research. Not my idea, not my style, but it's a thing.
  - Koshkin 7y ago
    Problem is, those who might need this sort of comparisons never read such articles. (Educated people already know what a nanometer is.)
- Iwan-Zotow 7y ago
  HOw many olympic size pools? Or football fields?

Animats 7y ago

This is either Nobel Prize material or total bullshit. Which is it? This could be a huge breakthrough in quantum computing. Or it could just be a capacitor with delusions of grandeur. Don't know.

jeeceebees 7y ago
Have all novel qubits gotten nobel prizes so far? I think there's more than enough room in between bullshit and nobel prize. This looks very promising, but as always the devil is in the details. The next steps are multiqubit gates, then linking those up into useful quantum circuits, and then hopefully doing actual quantum computations. Personally I wouldn't expect a nobel prize until one of those last 2 steps. There's a lot of hurdles before then to run into some nasty problems.
google234123 7y ago
Since they could only publish in Nature Communications it's probably BS.
- selimthegrim 7y ago
  See my comment above.
peacockwank 7y ago
lol, nah. I did my own PhD thesis a couple years ago on donor atoms in silicon, specifically selenium, forming hydrogen and helium like systems that "could" have been useful for forming a qbit. tldr selenium has 2 more valence electrons than silicon so when it is substitutionally doped into silicon then you get a helium like system, which in some cases ends up hydrogen like when, presumably, imperfections either local or remote cause enough disruption to whisk away/capture one of the electrons, thus forming a hydrogen like system. I didn't investigate the cause of the different molecular like complexes that spring up when you dope silicon like this though, I only probed things with light and did calculations relating to that probing, I didn't do any modelling concerning the diffusion and behaviour of dopants which I kinda regret. Then you can optically manipulate that remaining donor electron. It didn't really work cause it's hard and the lifetimes of the donor electron systems are not great (tens of ns to ~100ns for some of the systems). It was then I realised that physics research is a dangerous thing to attempt if you can't stomach the constant uncertainty and risk about your own personal future, when you are found to be not good enough due to not publishing, so I abandoned academia so I could massively reduce that stress and constant anxiety and actually have a life. So the tldr is that this is not bullshit at all, it is in-fact very interesting and a promising line of work. But it's not going to make anyone's career by itself, and without appropriate pumping of the importance of the work and sufficient mentoring no-one who works on it as a grad student has a future as a researcher. So no, it's neither Nobel Prize material or total bullshit.

the_dege 7y ago

I wasn't able to find it referenced in the article and on the paper, is it at room temperature or still near 0 °Kelvin?

tagrun 7y ago
The electron temperature should be around ~100mK