Abstract
Original language  English 

Awarding Institution 

Supervisors/Advisors 

Thesis sponsors  
Award date  19 Jun 2015 
Place of Publication  Enschede 
Publisher  
Print ISBNs  9789036539036 
DOIs  
Publication status  Published  19 Jun 2015 
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Keywords
 IR96299
 METIS310885
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Singlecharge tunneling in ambipolar silicon quantum dots. / Müller, Filipp.
Enschede : University of Twente, 2015. 135 p.Research output: Thesis › PhD Thesis  Research UT, graduation UT › Academic
TY  THES
T1  Singlecharge tunneling in ambipolar silicon quantum dots
AU  Müller, Filipp
N1  10.3990/1.9789036539036
PY  2015/6/19
Y1  2015/6/19
N2  Spin qubits in coupled quantum dots (QDs) are promising for future quantum information processing (QIP). A quantum bit (qubit) is the quantum mechanical analogon of a classical bit. In general, each quantum mechanical twolevel system can represent a qubit. For the spin of a single charge carrier e.g., which is a natural twolevel system, the basis quantum states are given by the spinup and the spindown state. QIP based on the spin degree of freedom requires long spin coherence times. Silicon provides an environment where spins can be controlled with minimal decoherence because of the weak hyperfine and spinorbit interaction. So far, most experiments have focused on electron spins, but hole spins offer great potential for spinbased QIP as well. A holespin qubit in silicon can benefit from its finite spinorbit coupling, because it allows efficient electricfield driven spin resonance applicable via local gate electrodes. However, it is still unclear whether the electron spin or the hole spin is most suitable as a qubit. We have developed an ambipolar metaloxidesemiconductor fieldeffect transistor (MOSFET)based device that allows the electron and the hole transport regime to be compared in one and the same nanostructure. We have investigated different types of devices. For all of them, we find the threshold voltage for the electron regime to be closer to zero than for the hole regime which, amongst others, can be ascribed to the ntype background doping of the nearintrinsic silicon wafer. We locally control the charge density by nanoscale bottom gates. Nonlinear transport measurements show singlecharge tunneling through QDs created underneath each bottom gate as well as between two bottom gates. Comparing the properties of the electron QD and the hole QD indicate that we load the same QD with either electrons or holes. Ambipolar QDs with singlecharge occupancy can break new ground in spinbased QIP, since they have the potential to act as a qubit comparator where the suitability of electronspin and holespin qubits can be evaluated in the same crystalline environment. Taking the advantages of either qubit one could think of future “quantum CMOS‿ technology based on ambipolar QDs.
AB  Spin qubits in coupled quantum dots (QDs) are promising for future quantum information processing (QIP). A quantum bit (qubit) is the quantum mechanical analogon of a classical bit. In general, each quantum mechanical twolevel system can represent a qubit. For the spin of a single charge carrier e.g., which is a natural twolevel system, the basis quantum states are given by the spinup and the spindown state. QIP based on the spin degree of freedom requires long spin coherence times. Silicon provides an environment where spins can be controlled with minimal decoherence because of the weak hyperfine and spinorbit interaction. So far, most experiments have focused on electron spins, but hole spins offer great potential for spinbased QIP as well. A holespin qubit in silicon can benefit from its finite spinorbit coupling, because it allows efficient electricfield driven spin resonance applicable via local gate electrodes. However, it is still unclear whether the electron spin or the hole spin is most suitable as a qubit. We have developed an ambipolar metaloxidesemiconductor fieldeffect transistor (MOSFET)based device that allows the electron and the hole transport regime to be compared in one and the same nanostructure. We have investigated different types of devices. For all of them, we find the threshold voltage for the electron regime to be closer to zero than for the hole regime which, amongst others, can be ascribed to the ntype background doping of the nearintrinsic silicon wafer. We locally control the charge density by nanoscale bottom gates. Nonlinear transport measurements show singlecharge tunneling through QDs created underneath each bottom gate as well as between two bottom gates. Comparing the properties of the electron QD and the hole QD indicate that we load the same QD with either electrons or holes. Ambipolar QDs with singlecharge occupancy can break new ground in spinbased QIP, since they have the potential to act as a qubit comparator where the suitability of electronspin and holespin qubits can be evaluated in the same crystalline environment. Taking the advantages of either qubit one could think of future “quantum CMOS‿ technology based on ambipolar QDs.
KW  IR96299
KW  METIS310885
U2  10.3990/1.9789036539036
DO  10.3990/1.9789036539036
M3  PhD Thesis  Research UT, graduation UT
SN  9789036539036
PB  University of Twente
CY  Enschede
ER 