Padawer-Blatt, A.; Ducatel, J.; Korkusinski, M.; Bogan, A.; Gaudreau, L.; Zawadzki, P.; Austing, D.G.; Sachrajda, A.S.; Studenikin, S.; Tracy, Lisa A.; Reno, J.; Hargett, Terry H.
Difference in g factors in multidot structures can form the basis of dot-selective spin manipulation under global microwave irradiation. Employing electric dipole spin resonance facilitated by strong spin-orbit interaction (SOI), we observe differences in the extracted values of the single-hole effective g factors of the constituent quantum dots of a GaAs/AlGaAs double quantum dot device at the level of ∼5%-10%. We examine the continuous change in the hole g factor with electrical detuning over a wide range of interdot tunnel couplings and for different out-of-plane magnetic fields. The observed tendency of the quantum dot effective g factors to steadily increase on decreasing the interdot coupling or on increasing the magnetic field is attributed to the impact on the SOI of changing the dot confinement potential and heavy-hole light-hole mixing.
Padawer-Blatt, Aviv P.; Ducatel, Jordan D.; Bogan, Alex B.; Austing, Guy D.; Gaudreau, Louis G.; Zawadzki, Piotr Z.; Sachrajda, Andrew S.; Studenikin, Sergei S.; Tracy, Lisa A.; Reno, John R.; Hargett, Terry H.
Bogan, Alex; Studenikin, Sergei; Korkusinski, Marek; Gaudreau, Louis; Phoenix, Jason; Zawadzki, Piotr; Sachrajda, Andy; Tracy, Lisa A.; Reno, J.L.; Hargett, Terry H.
We analyze experimentally and theoretically the transport spectra of a gated lateral GaAs double quantum dot containing two holes. The strong spin-orbit interaction present in the hole subband lifts the Pauli spin blockade and allows to map out the complete spectra of the two-hole system. By performing measurements in both source-drain voltage directions, at different detunings and magnetic fields, we carry out quantitative fitting to a Hubbard two-site model accounting for the tunnel coupling to the leads and the spin-flip relaxation process. We extract the singlet-triplet gap and the magnetic field corresponding to the singlet-triplet transition in the double-hole ground state. Additionally, at the singlet-triplet transition we find a resonant enhancement (in the blockaded direction) and suppression of current (in the conduction direction). The current enhancement stems from the multiple resonance of two-hole levels, opening several conduction channels at once. The current suppression arises from the quantum interference of spin-conserving and spin-flipping tunneling processes.
We report a detailed study of the tunnel barriers within a single-hole GaAs/AlGaAs double quantum dot device (DQD). For quantum information applications as well as fundamental studies, careful tuning and reliable measurements of the barriers are important requirements. In order to tune a DQD device adequately into the single-hole electric dipole spin resonance regime, one has to employ a variety of techniques to cover the extended range of tunnel couplings. In this work, we demonstrate four separate techniques, based upon charge sensing, quantum transport, time-resolved pulsing, and electron dipole spin resonance spectroscopy to determine the couplings as a function of relevant gate voltages and magnetic field. Measurements were performed under conditions of both symmetric and asymmetric tunnel couplings to the leads. Good agreement was observed between different techniques when measured under the same conditions. The results indicate that even in this relatively simple circuit, the requirement to tune multiple gates and the consequences of real potential profiles result in non-intuitive dependencies of the couplings as a function of the plunger gate voltage and the magnetic field.
There is rapidly expanding interest in exploiting the spin of valence-band holes rather than conduction-band electrons for spin qubit semiconductor circuits composed of coupled quantum dots. The hole platform offers stronger spin-orbit interaction (SOI), large difference between in-dot-plane and out-of-dot-plane g-factors, i.e. g-factor anisotropy, and a significantly reduced hyperfine coupling to nuclei in the host material. These attributes collectively can deliver fast all-electric coherent spin manipulation, efficient spin-flip inter-dot tunneling channels, a voltage tunable effective g-factor, a g-factor adjustable to nearly zero in an appropriately oriented external magnetic field, and long spin relaxation and coherence times. Here, we review our recent work on the physics of heavy holes confined in a planar GaAs/AlGaAs double quantum dot system with strong SOI. For a single-hole, we have performed resonant tunneling magneto-spectroscopy to extract spin-flip and spin-conserving tunneling strengths, implemented spin-flip Landau-Zener-Stückelberg-Majorana (LZSM) interferometry, determined the spin relaxation time T 1 as a function of magnetic field using a fast single-shot latched charge technique, electrically tuned the effective g-factor revealed by electric dipole spin resonance, and found signatures of the hyperfine interaction and dynamic nuclear polarization with holes. For two-holes, we have measured the energy spectrum in the presence of strong SOI (and so not limited by Pauli spin blockade), quantified the heavy-hole (HH) g-factor anisotropy on tilting the magnetic field, described a scheme to employ HHs whose g-factor is tunable to nearly zero for an in-plane magnetic field for a coherent photon-to-spin interface, and observed a well-defined LZSM interference pattern at small magnetic fields on pulsing through the singlet-triplet anti-crossing.
Studenikin, Sergei S.; Korkusinski, Marek K.; Austing, Guy D.; Gaudreau, Louis G.; Zawadski, Piotr Z.; Sachrajda, Andy S.; Ducatel, Jordan D.; Padawer-Blatt, Aviv P.; Bogan, Alex B.; Takahashi, Motoi T.; Coish, Bill C.; Philippopoulos, Pericles P.; Hirayama, Yoshiro H.; Reno, J.L.; Tracy, Lisa A.; Hargett, Terry H.
Studenikin, Sergei S.; Austing, Guy D.; Sachrajda, Andrew S.; Ducatel, Jordan D.; Padawer-Blatt, Aviv P.; Bogan, Alex B.; Takahashi, Motoi T.; Tracy, Lisa A.; Reno, J.L.; Hargett, Terry H.; Coish, Bill C.; Philippopoulos, Pericles P.
Sachrajda, Andrew S.; Studenikin, Sergei S.; Austing, Guy D.; Gaudreau, Louis G.; Zawadski, Piotr Z.; Bogan, Alex B.; Takahashi, Motoi T.; Ducatel, Jordan D.; Padawer-Blatt, Aviv P.; Tracy, Lisa A.; Reno, J.L.; Hargett, Terry H.
Hole spins have recently emerged as attractive candidates for solid-state qubits for quantum computing. Their state can be manipulated electrically by taking advantage of the strong spin-orbit interaction (SOI). Crucially, these systems promise longer spin coherence lifetimes owing to their weak interactions with nuclear spins as compared to electron spin qubits. Here we measure the spin relaxation time T1 of a single hole in a GaAs gated lateral double quantum dot device. We propose a protocol converting the spin state into long-lived charge configurations by the SOI-assisted spin-flip tunneling between dots. By interrogating the system with a charge detector we extract the magnetic-field dependence of T1 ∝ B−5 for fields larger than B = 0.5 T, suggesting the phonon-assisted Dresselhaus SOI as the relaxation channel. This coupling limits the measured values of T1 from ~400 ns at B = 1.5 T up to ~60 μs at B = 0.5 T.
Takahashi, Motoi T.; Studenikin, Sergei S.; Austing, Guy D.; Bogan, Alex B.; Gaudreau, Louis G.; Zawadski, Piotr Z.; Tracy, Lisa A.; Hargett, Terry H.; Reno, J.L.; Sachrajda, Andrew S.
Studenikin, Sergei S.; Austing, Guy D.; Gaudreau, Louis G.; Zawadski, Piotr Z.; Bogan, Alex B.; Ducatel, Jordan D.; Padawder-Blatt, Aviv P.; Tracy, Lisa A.; Reno, J.L.; Hargett, Terry H.
Studenikin, Sergei S.; Bogan, Alex B.; Takahashi, Motoi T.; Austing, Guy D.; Gaudreau, Louis G.; Zawadski, Piotr Z.; Sachrajda, Andy S.; Tracy, Lisa A.; Hargett, Terry H.; Reno, J.L.
Sachrajda, Andrew S.; Bogan, Alex B.; Studenikin, Sergei S.; Gaudreau, Louis G.; Takahashi, Motoi T.; Austing, Guy D.; Korkusinski, Marek K.; Ares, Geof A.; Tracy, Lisa A.; Reno, J.L.; Hargett, Terry H.
We demonstrate ultra-low power cryogenic high electron mobility transistor (HEMT) amplifiers for measurement of quantum devices. The low power consumption (few uWs) allows the amplifier to be located near the device, at the coldest cryostat stage (typically less than 100 mK). Such placement minimizes parasitic capacitance and reduces the impact of environmental noise (e.g. triboelectric noise in cabling), allowing for improvements in measurement gain, bandwidth and noise. We use custom high electron mobility transistors (HEMTs) in GaAs/A1GaAs heterostructures. These HEMTs are known to have excellent performance specifically at mK temperatures, with electron mobilities that can exceed 10 6 cm 2 /Vs, allowing for large gain with low power consumption. Low temperature measurements of custom HEMT amplifiers at T = 4 K show a current sensitivity of 50 pA at 1 MHz bandwidth for 5 mW power dissipation, which is an improvement upon performance of amplifiers using off-the-shelf HEMTs.
Sachrajda, Andrew S.; Bogan, Alex B.; Studenikin, Sergei S.; Gaudreau, Louis G.; Tracy, Lisa A.; Reno, J.L.; Hargett, Terry H.; Korkusinski, Marek K.; Aers, Geof A.
We perform Landau-Zener-Stückelberg-Majorana (LZSM) spectroscopy on a system with strong spin-orbit interaction (SOI), realized as a single hole confined in a gated double quantum dot. Analogous to electron systems, at a magnetic field B=0 and high modulation frequencies, we observe photon-assisted tunneling between dots, which smoothly evolves into the typical LZSM funnel-shaped interference pattern as the frequency is decreased. In contrast to electrons, the SOI enables an additional, efficient spin-flip interdot tunneling channel, introducing a distinct interference pattern at finite B. Magnetotransport spectra at low-frequency LZSM driving show the two channels to be equally coherent. High-frequency LZSM driving reveals complex photon-assisted tunneling pathways, both spin conserving and spin flip, which form closed loops at critical magnetic fields. In one such loop, an arbitrary hole spin state is inverted, opening the way toward its all-electrical manipulation.
Studenikin, Sergei S.; Bogan, Alex B.; Gaudreau, Louis G.; Korkusinski, Marek K.; Zawadski, Piotr Z.; Tracy, Lisa A.; Reno, J.L.; Hargett, Terry H.; Sachrajda, Andrew S.
Sachrajda, Andrew S.; Bogan, Alex B.; Studenikin, Alex S.; Korkusinski, Marek K.; Aers, Geoff A.; Gaudreau, Louis G.; Zawadski, Piotr Z.; Tracy, Lisa A.; Reno, J.L.; Hargett, Terry H.
Korkusinski, Marek K.; Bogan, Alex B.; Studenikin, Sergei S.; Aers, Geoff A.; Gaudreau, Louis G.; Zawadski, Piotr Z.; Sachrajda, Andrew S.; Tracy, Lisa A.; Reno, J.L.; Hargett, Terry H.
Sachrajda, Andrew S.; Bogan, Alex B.; Studenikin, Sergei S.; Korkusinski, Marek K.; Aers, Geoff A.; Gaudreau, Louis G.; Zawadski, Piotr Z.; Tracy, Lisa A.; Reno, J.L.; Hargett, Terry H.