PDF (double-sided) - Physics Department, UCSB - University of ...
PDF (double-sided) - Physics Department, UCSB - University of ... PDF (double-sided) - Physics Department, UCSB - University of ...
Figure 4.4: Spice Coupler Design – a) Schematic: The qubit is emulated by a damped LC oscillator. One qubit is driven with a microwave source and the response of the second qubit is analyzed. b) Analysis: The resulting response curve shows a splitting that is equal to the coupling strength. to each other. The simplest way to design a coupling element is via the use of circuit modeling software like SPICE. For this purpose, the qubit can be emulated simply via a parallel RLC oscillator with its electrical values chosen to adjust its resonance frequency to the qubit’s operating frequency. One of the qubits can then be driven with an AC voltage and the response of the second qubit to this bias can be measured. Figure 4.4b shows the frequency response of the second qubit to a drive on the first. In this case, the two qubits are coupled through an LC oscillator as shown in Figure 4.4a. This trace shows a response peak that is split by about 20 MHz. This splitting gives a fairly good estimate of the coupling strength that this element will yield in the final qubit circuit. 80
Figure 4.5: Qubit Integrated Circuit: The qubit circuit is placed inside a cutout in the IC’s ground-plane. The geometrical arrangement of the qubit, squid, and flux bias coils determine their mutual inductances. The layout has three terminals to connect the squid bias, flux bias, and qubit coupler. 4.2 Geometric Circuit Element Layout Now that all electrical design values are chosen, the next step is to lay out how the elements will be implemented. For almost all elements, their electrical characteristics are primarily determined by their geometric shape. 81
- Page 57 and 58: the cosine forms a local minimum al
- Page 59 and 60: Figure 2.5: Example Qubit Coupling
- Page 61 and 62: Readout schemes can further be cate
- Page 63: states in the qubit’s inductor, t
- Page 66 and 67: at time t. r is not restricted to b
- Page 68 and 69: 3.1.2 Effects of a Time Dependent P
- Page 70 and 71: In some cases, it is possible to so
- Page 72 and 73: Figure 3.1: Examples of Numerical S
- Page 74 and 75: • The energy difference between t
- Page 76 and 77: like this: V = ( V (−1, −1), V
- Page 78 and 79: Figure 3.2: Simulation of LC Oscill
- Page 80 and 81: Table 3.1: Transition Matrix Elemen
- Page 82 and 83: with ω mn = Em−En . Multiplying
- Page 84 and 85: α, it can be ignored. Thus, the in
- Page 86 and 87: e solved exactly: A(t + ∆t) = e
- Page 88 and 89: qubits would be simulated using: A(
- Page 90 and 91: This calculation assumes that the s
- Page 92 and 93: Decoherence consists of two parts:
- Page 94 and 95: Note the difference in signs of the
- Page 97 and 98: Chapter 4 Designing the Phase Qubit
- Page 99 and 100: mutual inductance between the qubit
- Page 101 and 102: During the measurement, the | 1 〉
- Page 103 and 104: the right impedance transformation
- Page 105 and 106: excitations. Since these are a pote
- Page 107: Figure 4.3: Squid I/V Traces - a) L
- Page 111 and 112: The geometry of the qubit junction
- Page 113 and 114: squid loop. Thus, this tool can be
- Page 115: now, amorphous silicon seems to pro
- Page 118 and 119: Figure 5.1: L-Edit Mask Layout Tool
- Page 120 and 121: Figure 5.2: Fabrication Building Bl
- Page 122 and 123: Figure 5.3: Photolithography and Et
- Page 124 and 125: times the removal can be a bit tric
- Page 126 and 127: Figure 5.4: Clearing Vias from Nati
- Page 128 and 129: 5.6 Junction Layers 5.6.1 Oxidation
- Page 130 and 131: top wiring layer to protect all low
- Page 132 and 133: 104
- Page 134 and 135: 6.1 Physical Quality Control during
- Page 136 and 137: 6.1.3 Atomic Force Microscopy To re
- Page 138 and 139: Figure 6.1: 4-Wire Measurement - a)
- Page 140 and 141: 6.3 Quantum Measurements at 25 mK 6
- Page 142 and 143: seems to be a box machined out of s
- Page 144 and 145: Figure 6.2: Dilution Refrigerator W
- Page 146 and 147: cessing data. This protects the vol
- Page 148 and 149: 6.3.9 Anritsu Microwave Source The
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- Page 152 and 153: ment, the scalability requirements,
- Page 154 and 155: people without any formal training
- Page 156 and 157: 7.2.4 Performance Last, but certain
Figure 4.4: Spice Coupler Design – a) Schematic: The qubit is emulated by a<br />
damped LC oscillator. One qubit is driven with a microwave source and the<br />
response <strong>of</strong> the second qubit is analyzed. b) Analysis: The resulting response<br />
curve shows a splitting that is equal to the coupling strength.<br />
to each other. The simplest way to design a coupling element is via the use <strong>of</strong><br />
circuit modeling s<strong>of</strong>tware like SPICE. For this purpose, the qubit can be emulated<br />
simply via a parallel RLC oscillator with its electrical values chosen to adjust its<br />
resonance frequency to the qubit’s operating frequency. One <strong>of</strong> the qubits can<br />
then be driven with an AC voltage and the response <strong>of</strong> the second qubit to this<br />
bias can be measured. Figure 4.4b shows the frequency response <strong>of</strong> the second<br />
qubit to a drive on the first. In this case, the two qubits are coupled through an<br />
LC oscillator as shown in Figure 4.4a. This trace shows a response peak that is<br />
split by about 20 MHz. This splitting gives a fairly good estimate <strong>of</strong> the coupling<br />
strength that this element will yield in the final qubit circuit.<br />
80
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