Fast Hole Tunneling Times in Germanium Hut Wires Probed by Single-Shot Reflectometry.

Lada Vukušić,Josip Kukučka,Hannes Watzinger,Georgios Katsaros

doi:10.1021/acs.nanolett.7b02627

Lada Vukušić, Josip Kukučka + Show 2 more

Open Access

https://doi.org/10.1021/acs.nanolett.7b02627

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Abstract

Heavy holes confined in quantum dots are predicted to be promising candidates for the realization of spin qubits with long coherence times. Here we focus on such heavy-hole states confined in germanium hut wires. By tuning the growth density of the latter we can realize a T-like structure between two neighboring wires. Such a structure allows the realization of a charge sensor, which is electrostatically and tunnel coupled to a quantum dot, with charge-transfer signals as high as 0.3 e. By integrating the T-like structure into a radiofrequency reflectometry setup, single-shot measurements allowing the extraction of hole tunneling times are performed. The extracted tunneling times of less than 10 μs are attributed to the small effective mass of Ge heavy-hole states and pave the way toward projective spin readout measurements.

Highlights

Heavy holes confined in quantum dots are predicted to be promising candidates for the realization of spin qubits with long coherence times
By tuning the growth density of the latter we can realize a T-like structure between two neighboring wires. Such a structure allows the realization of a charge sensor, which is electrostatically and tunnel coupled to a quantum dot, with charge-transfer signals as high as 0.3 e
By integrating the T-like structure into a radiofrequency reflectometry setup, single-shot measurements allowing the extraction of hole tunneling times are performed

Summary

Nano Letters

Between the gate and the end of the wire; its hole occupation is to be determined with the SHT sensor coupled to it. The pulse was applied along the upper part of the break in the Coulomb peak of the SHT shown in Figure 2b (black solid line) This diagonal pulsing is achieved by applying the pulse both to the dot and to the sensor gate simultaneously, but with a different sign and with a different amplitude. A threepart voltage pulse was applied along the lower part of the break in the Coulomb peak in Figure 2b (black dashed line) in order to load (pink hexagon in Figure 2b) and unload Negative voltage pulse part, a hole is loaded into the dot (pink hexagon in Figure 2b); the reflected signal from the sensor reaches its maximum. The observed large charge transfer signals and the extracted hole tunneling times of a few microseconds pave the way toward projective spin readout measurements.

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