Ph.D. Thesis - Physics

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Figure 6-10: <strong>Ph</strong>otograph of the surface-electrode PCB trap, known as “Bastille,” used for ablation loading experiments. The rf electrodes are spaced by 2 mm center to center, leading to an ion height above the surface of 0.8 mm, as predicted by numerical modeling. The long center electrode is held at rf ground, but may have a dc offset applied to it. The segmented electrodes on the sides carry dc potentials for confinement along the long axis of the trap, as well as elimination of stray electric fields. The wirebonds visible on the edge of the electrodes connect them to gold pads on the CPGA chip carrier. To summarize this section, a PCB ion trap was loaded with the aid of buffer gas using electron impact ionization. The buffer gas allows sufficient ion signal and lifetimes to perform compensation measurements before loading in UHV with reasonable lifetimes (O(minutes)) is achieved. There are two primary lessons from this work: the first is that exposure to dielectric must be minimized to limit the surface area that can trap charges that act on the ions; the second is that methods for loading ions must be found that lead to less accumulation of charge. Buffer-gas loading was a useful expedient in this work, but is not ideal as a long-term solution, since it results in a much higher UHV pressure than is possible without it. We therefore turn to a different ion trap setup and study ablation loading of surface- electrode traps. 6.4 The second-generation PCB ion trap Follwing successful trapping in San Quentin, we produced a new surface-electrode PCB trap. This trap, known as “Bastille,” has become a real “workhorse” to us, since it traps so reliably that it may be used first in a new apparatus to verify that everything else is working before a new trap is tested. In this section we present the design of this trap, a photograph of which is shown in Fig. 6-10. 142
Figure 6-11: Bastille mounted in the CPGA. The noteworthy features of this trap compared to San Quentin are as follows. The gaps between rf and dc electrodes are 0.5 mm, compared to 0.83 mm. This is the minimum width machinable by our manufacturer, Hughes Circuits. The ground electrode extends all the way around the segmented dc electrodes. This can help prevent neutral atom flux from the oven from shorting the dc electrodes together; atoms primarily come from the side (ˆx direction), but with this feature, only atoms with a velocity component along the ˆy direction can cause shorting. Aside from that, the whole trap is somewhat smaller in scale. The trap is polished using a process similar to that of San Quentin, but the mounting process is quite different. The trap is mounted in a ceramic pin grid array (CPGA) chip carrier, like that used in Ch. 5. The trap is held above the center gold pad of the CPGA by 1 mm thick glass slides; UHV-compatible epoxy (EpoTek 353ND) holds it together. Wirebonds connect the trap electrodes to gold pads on the CPGA, which connect to pins on the underside of the chip carrier. These fit in a socket that connects to the electrical feedthrough. A photograph of the trap mounted in the CPGA is given in Fig. 6-11. 6.5 Ablation loading of planar PCB ion traps In this section we present our work on loading ion traps using laser ablation. Ablation is a process in which a high-energy pulsed laser is used to eject high-energy material, including neutral atoms, ions, electrons, and molecules, from the surface of a solid. It has found wide usage in the physical chemistry community for producing molecules to be studied with laser spectroscopy or mass spectrometry [<strong>Ph</strong>i07], and has had some limited usage in the ion trapping community. Laser ablation of a solid target has been used to load ion traps as early as 1981 [KGF + 90]. In contrast to other methods of loading ion traps, atoms are not ionized once already inside the trap region. Instead, a pulse of high-energy electrons from the ablation plume reaches the trap first, shorting it out for a time of O(10µs). While the trapping potentials are thus 143
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An Investigation of Precision and S
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Acknowledgments What a long, strang
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should totally start a band. I also
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2.4 Conclusions and further questio
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7.6.1 Regular array of stationary q
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List of Figures 2-1 The CNOT gate i
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7-12 Magnetic fields due to a “tr
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Chapter 1 Introduction The growth o
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1.1 Quantum information The concept
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us whether the target system obeys
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Nevertheless, there are a number of
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Digital Analog Classical Quantum Sp
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electrodes [TKK + 99]. This heating
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Digital Analog Classical Quantum Sp
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2. Initialization to a simple fiduc
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qubits, and in Ref. [SGA + 05] in t
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the lattice architecture, we discov
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1.6 Contributions to this work In t
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5) Ref. [DLC + 09b] Wiring up trapp
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Chapter 2 Quantum simulation using
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µN the nuclear magneton, and B0 th
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⎡ ⎤ a 0 0 0 ⎢ ⎥ ⎢ ρ2 =
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The same effect as number 2 above i
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where V0 is the maximum signal stre
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actions that occur between nuclei i
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Figure 2-2: The 2,3-dibromothiophen
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detail how this was done with a sim
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and thus requires invocation of the
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Renormalization Group (DMRG), with
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3.3 The bounds on precision In this
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Figure 3-1: A schematic of a generi
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Figure 3-3: The 11.7 T, 500 MHz sup
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. Figure 3-4: The above probe is a
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Figure 3-5: The CHFBr2 molecule. Al
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Figure 3-6: Frequency-domain spectr
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used to extract the answer is irrel
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Chapter 4 Theory and history of qua
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GND RF r ENDCAP 0 z 0 ENDCAP Ring T
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where Q is the charge of the trappe
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angular momentum along the quantiza
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Page 93 and 94: selection rule ∆m = ±1 is applie
Page 95 and 96: Figure 4-3: Schematic diagram of sp
Page 97 and 98: to address an ion in state |↑〉
Page 99 and 100: the vibrational temperature is low.
Page 101 and 102: to the design of the trap itself. M
Page 103 and 104: to the quantum-mechanical ground st
Page 105 and 106: Chapter 5 Lattice ion traps for qua
Page 107 and 108: Figure 5-1: Schematic of the lattic
Page 109 and 110: Figure 5-3: Fit to Eq. 5.2 of the C
Page 111 and 112: Figure 5-4: The vacuum chamber for
Page 113 and 114: weeks. Low pressures depend on choo
Page 115 and 116: Figure 5-5: Left: Level diagram for
Page 117 and 118: Figure 5-7: (a) Schematic of the cr
Page 119 and 120: (a) Lattice Trap Schematic TOP PLAT
Page 121 and 122: mix the microspheres evenly in the
Page 123 and 124: Using the expression for ωˆr deri
Page 125 and 126: Figure 5-15: Plot of the motional c
Page 127 and 128: Figure 5-17: Dependence of the trap
Page 129 and 130: Chapter 6 Surface-electrode PCB ion
Page 131 and 132: Figure 6-1: Schematic of a linear i
Page 133 and 134: Figure 6-2: Layout of the trap elec
Page 135 and 136: Figure 6-3: Above are the cross sec
Page 137 and 138: Figure 6-6: Photograph of the trap
Page 139 and 140: Figure 6-8: CCD image of a cloud of
Page 141: Figure 6-9: Measurement results sho
Page 145 and 146: Figure 6-13: A diagram of the setup
Page 147 and 148: Figure 6-14: A plot of the trapped
Page 149 and 150: allows us to upper-bound the amount
Page 151 and 152: Chapter 7 Quantum simulation in sur
Page 153 and 154: Figure 7-1: Left: Uraniborg 1, as r
Page 155 and 156: Figure 7-3: Calculated secular freq
Page 157 and 158: Figure 7-5: Left: Structure of 2-D
Page 159 and 160: Figure 7-7: Scaling of the order of
Page 161 and 162: involved. Because ions near the cen
Page 163 and 164: Results Before presenting the numer
Page 165 and 166: Figure 7-10: Calculation results fo
Page 167 and 168: 7.3 Magnetic gradient forces Now th
Page 169 and 170: Figure 7-13: Scaling of the J-coupl
Page 171 and 172: how are single-ion operations to be
Page 173 and 174: 250 psi, which increases to around
Page 175 and 176: Figure 7-18: At the center of this
Page 177 and 178: Figure 7-19: The plastic socket tha
Page 179 and 180: Figure 7-21: The two internal lense
Page 181 and 182: Figure 7-22: Measured secular frequ
Page 183 and 184: Along ˆy, the spacing is dˆy = 28
Page 185 and 186: of O2 to 2 × 10 −12 torr. Decohe
Page 187 and 188: Part III Toward ion-ion coupling ov
Page 189 and 190: Chapter 8 Motivation for and theory
Page 191 and 192: Figure 8-1: Schematic of the experi
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are in close agreement in the case
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8.2.3 Simulated coupling rates We n
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Johnson noise We begin our discussi
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should suffice. Note that the above
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Chapter 9 Measuring the interaction
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Figure 9-2: Left: Level diagram for
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Figure 9-5: Photograph of the micro
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A fit of the resulting curve return
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Figure 9-9: Linear fit of the ωˆy
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Figure 9-12: Heating rate as determ
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Chapter 10 Conclusions and outlook
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traps, linking ions using photons,
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Bibliography [ADM05] Paul M. Alsing
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[CGB + 94] J. I. Cirac, L. J. Garay
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[GME + 02] M. Greiner, O. Mandel, T
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[LCL + 07] D. R. Leibrandt, R. J. C
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[PC04a] D. Porras and J. I. Cirac.
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[TBZ05] L. Tian, R. Blatt, and P. Z
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Appendix A Matlab code for Ising mo
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err_result = mean(theerr) 231
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J = J0; Jt(1) = J; Bt(1) = B; for k
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A.3 Simulation with constant force
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Appendix B Mathematica code for ion
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2 crystal_shape_6uraniborg.nb Out[6
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Appendix C How to trap ions in a cl
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Finally, we note that the chilled w
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C.4 Laser alignment and imaging As
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