ELFT HÍRADÓ

[Janos Asboth <asboth.janos AT ttk.bme.hu>]

Meghívó

BME Elméleti Fizika Szeminárium,

ápr  21. péntek 10h15,

1111 Budapest, Budafoki út 8., BME F III. magasföldszint 01.,
Elméleti Fizika Tanszék szemináriumi szoba

Stefano Bosco (Basel University):

*Theory of hole spin qubits in silicon and germanium quantum dots*


Hole spin qubits in silicon and germanium quantum dots are promising
platforms for large-scale quantum computers because of their large
intrinsic spin-orbit
interaction, which permits efficient and ultrafast all-electric qubit
control without additional components.

I will present schemes to engineer this interaction in different
architectures, e.g. in the squeezed Ge quantum dots proposed in [1], aiming
to optimize quantum information processing. A large spin-orbit interaction
mediates a strong coupling between hole spins and microwave photons. Hole
spin-photon coupling is not only strong but is also electrically tunable
and can be engineered to be longitudinal [2], where the microwave field
couples to the phase of the spin. This type of coupling enables exact
protocols for fast and high-fidelity two-qubit gates that could even work
at high temperatures.

On the other hand, the spin-orbit interaction also couples the spin to
charge noise, causing the qubit to decohere. To overcome this issue, I will
discuss qubit designs that enable sweet spots where charge noise can be
completely removed [3]. These sweet spots appear in hole spin qubits
encoded in silicon fin field-effect transistors, devices commonly used in
the modern semiconductor industry. In these qubits, the noise caused by
hyperfine interactions with nuclear spins -another leading source of
decoherence in spin qubits- is also strongly suppressed, greatly enhancing
their coherence, and reducing the need for expensive isotopically purified
materials [4].

Moreover, the large spin-orbit interaction in hole quantum dots enables
phenomena that are out of reach in competing architectures. For example, in
these systems the exchange interactions between nearby spins can be
highly anisotropic, even at zero magnetic fields, opening the way to novel
protocols to enhance the speed and fidelity of two-qubit gates in future
quantum processors.


*[1] Bosco et al (2021) PRB 104*

*[2] Bosco et al (2022) PRL 129*

*[3] Bosco Hetenyi Loss (2021) PRX Quantum 2*

*[4] Bosco and Loss (2021) PRL 127*

Minden érdeklődőt szeretettel várunk.
Asbóth János,
 szemináriumi koordinátor