1. Single Electron Transistors and Quantum Computers
4/1/2017 6:27 AM
Single Electron Transistors and Quantum Computers
G5: Norma L. Rangel
Nanotechnology
4/20/2010
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

2. Overview of Nano-electronic devices
Ellenbogen 2000

3. Outline Conventional Transistors Single Electron Transistors
4/1/2017 6:27 AM
Outline
Conventional Transistors
Single Electron Transistors
Coulomb Island
Coulomb Blockade
Coulomb Gap Energy
Tunneling
Applications of SETs
Quantum Computers: NATURE, Vol 464,
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

4. Fundamental component in almost all electronic devices
Transistors
Transistors
BJT
NPN
Electrons
PNP
holes
FET
JFET
MOSFET
Fundamental component in almost all electronic devices
A transistor can be used as a switch and as amplifier
Manufactured in different shapes but they have three leads: BASE (gate controller device), COLLECTOR (larger electrical supply, source) AND EMITTER (the outlet for that supply)

5. Junction transistors & field effect transistors
A junction transistor: a thin piece of one type of semiconductor material between two thicker layers of the opposite type.
A field effect transistor: Electricity flows through one of the layers, called the channel. The voltage connected to the gate controls the strength of the current in the channel.

6. Single Electron Transistor (SET)
Switching device that uses controlled electron tunneling to amplify current.
A SET is made from two tunnel junctions that share a common electrode.
An AFM picture of a single-electron transistor (SET).
The red region, the island where only single electrons may be admitted.
Schumacher et al.,  Applied Physics Letters

7. Single Electron Transistor (SET) Tunnel Junction
A tunnel junction consists of two pieces of  metal  separated by a very thin (~1 nm) insulator.
The only way for electrons in one of the metal electrodes to travel to the other electrode is to tunnel through the insulator.
Since tunneling is a discrete process, the electric charge that flows through the tunnel junction flows in multiples of e, the charge of a single electron.

8. Single Electron Transistor (SET) Tunneling
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Single Electron Transistor (SET) Tunneling
Quantum tunneling refers to the phenomena of a particle's ability to penetrate energy barriers within electronic structures.
Schematic representation of quantum tunnelling through a barrier.
The energy of the tunneled particle is the same, only the quantum amplitude (and hence the probability of the process) is decreased.
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

9. Dynamics of SET
The SET is made by placing 2 tunnel junctions in series
The 2 tunnel junction create what is known as a “Coulomb Island” that electrons can only enter by tunneling through one of the insulators.
This device has 3 terminals like the FETs.
The cap may seem like a third tunnel junction, but is much thicker than the others so that no electrons could tunnel through it.
The cap simply serves as a way of setting the electric charge on the coulomb island.
controlled by light irradiation

10. Coulomb Island
When a capacitor is charged through a resistor, the charge on the capacitor is proportional to the applied voltage and shows no sign of quantization.
When a tunnel junction replaces the resistor, a conducting island is formed between the junction and the capacitor plate. In this case the average charge on the island increases in steps as the voltage is increased -> Low self capacitance
The steps are sharper for more resistive barriers and at lower temperatures.

11. Procedure Charge passes through the island in quantized units.
The energy must equal the coulomb energy e^2/2Cg.
Coulomb blockade, As the bias voltage between the source and drain is increased, an electron can pass through the island when the energy in the system reaches the coulomb energy.
The critical voltage needed to transfer an electron onto the island equal to e/C, is called the coulomb gap energy.

12. Coulomb Blockade
The effect in which electron can not pass through the island unless the energy in the system is equal to the coulomb energy e^2/Cg.
The thermal energy kBT must be below the charging energy or the electron will be able to pass the quantum blockade via thermal excitation
Coulomb blockade tries to alleviate any leak by current during the off state of the SET.

13. For Function SETs
Capacitance of the island must be less than 10^-17 Farads and therefore its size must be smaller that 10 nm.
The wavelength of the electrons is comparable with the size of the dot, which means that their confinement energy makes a significant contribution to the coulomb energy.

14. Example SET Fabrication
Localization of appropriate
flakes with optical microscope
Contacting with metal electrodes
by e-beam Lithography
Writing an etch-mask with e-beam lithography
Reactive ion etching with Ar/O2 plasma
Wire-bonding to contact pins -> testing the device
Further etching, if necessary to narrow the graphene structures

15. Example: Graphene SET
Conductance G of a device with the central island as a function of Vg in the vicinity
T = 0.3 K
Chaotic Dirac Billiard in Graphene Quantum Dots
L. A. Ponomarenko, F. Schedin, M. I. Katsnelson, R. Yang,1 E. W. Hill, K. S. Novoselov, A. K. Geim
Science 2008

16. Quantum Computers Review Article NATURE, March 2010
T. D. Ladd, F. Jelezko, R. Laflamme, Y. Nakamura, C. Monroe & J. L. O’Brien
NATURE, March 2010

17. I think I can safely say that nobody understands quantum mechanics.
“No, you’re not going to be able to understand it You see, my physics students don’t understand it either. That is because I don’t understand it. Nobody does. ... The theory of quantum electrodynamics describes Nature as absurd from the point of view of common sense. And it agrees fully with an experiment. So I hope that you can accept Nature as She is -- absurd.
Richard Feynman

18. Quantum Computer:
A machine that would exploit the full complexity of a many-particle quantum wavefunction to solve a computational problem.
A quantum computer will not be a faster, bigger or smaller version of an ordinary computer. Rather, it will be a different kind of computer, engineered to control coherent quantum mechanical waves for different applications.

19. Light to laser - Computer to QC
Light was always ‘incoherent’, meaning that the many electromagnetic waves generated by the source were emitted at completely random times with respect to each other.
Quantum mechanical effects, however, allow these waves to be generated in phase, and the light source engineered to exploit this concept was the laser.
Before the invention of the laser we had technological advances in making light: fire, the lantern, the lightbulb. Until the laser, however,
this light was always ‘incoherent’, meaning that the many electromagnetic waves generated by the source were emitted at completely random times with respect to each other.

20. Bits and Qubits
Classical Computation:
Classical logic bit: “0” and “1”
Quantum Computation:
Quantum bit, “Qubit”, can be manipulated using the rules of quantum physics
To build a quantum computer, need many qubits with long coherence times
Need interactions between qubits to generate entanglement

21. Quantum State

22. Two Distinguishable States 

23. Continuous State Space + b 
Orthogonal quantum states |0> , |1> and their superposition |Ψ> = c0|0> + c1|1>

24. Potential technologies of QC
Shor’s quantum algorithm for factoring large numbers. Grover’s Search Algorithm
Artificial nanotechnology: we might use quantum computers to understand and engineer such technology at the atomic level.
Quantum communication: sharing of secrets with security guaranteed
Quantum metrology: in which distance and time could be measured with higher precision than is possible otherwise.
Quantum teleportation
Factoring large numbers
Fast database searches
Simulation of quantum systems

25. Quantum teleportation
Entanglement-assisted teleportation, is a technique used to transfer quantum information from one quantum system to another.
Is a quantum protocol by which a qubit a (the basic unit of quantum information) can be transmitted exactly (in principle) from one location to another.

26. QC Hardware QC Software
Many materials under consideration: Quantum bits are often imagined to be constructed from the smallest form of matter, an isolated atom, as in ion traps and optical lattices, but they may likewise be made far larger than routine electronic components, as in some superconducting systems.
QC Software
Nielsen, M. A. & Chuang, I. L. Quantum Computation and Quantum Information (Cambridge University Press, 2000).

27. Implementation of quantum computers: DiVincenzo’s criteria
1. Scalability: A scalable physical system with well characterized parts, usually qubits.
2. Initialization: The ability to initialize the system in a simple “pure” state.
3. Control: The ability to control the state of the computer using sequences of elementary universal gates.
4. Stability: Long decoherence times, together with the ability to suppress decoherence through error correction and fault-tolerant computation.
5. Measurement: The ability to read out the state of the computer in a convenient product basis.
DiVincenzo, Fortschr. Phys. 48, 771 (2000)

28. Dephasing and Decoherence
An oscillator with frequency varying by trial, as indicated by the differently colored waves, averages to an oscillation decaying with apparent dephasing timescale T2*.
A quantum oscillator interacting with the environment may have phase-kicks in a single trial; these are the processes that harm coherence in quantum computation, and lead to an average decay process of timescale T2.

29. Decoherence
Qubit decoherence can be related to noise in the environment coupled to qubit.
Relaxation of non-thermal distribution.
Decay rate of resonance peaks
Dephasing caused by impedance both at level splitting and zero frequency.
Width of resonance peaks

30. ERRORS Quantum error correction’ (QEC): N Fault-tolerant
No system is fully free of decoherence, but small amounts of decoherence may be removed through various techniques
Fault-tolerant
for error probabilities beneath a critical threshold that depends on the computer hardware, the sources of error, and the protocols used for QEC.

31. Physical requirements
Scalability. The computer must operate in a Hilbert space whose dimensions can grow exponentially without an exponential cost in resources (such as time, space or energy).
Universal logic. The large Hilbert space must be accessible using a finite set of control operations; the resources for this set must also not grow exponentially.
Correctability. It must be possible to extract the entropy of the computer to maintain the computer’s quantum state.
It extends the methods of vector algebra and calculus from the two-dimensional Euclidean plane and three-dimensional space to spaces with any finite or infinite number of dimensions. A Hilbert space is an abstract vector space possessing the structure of an inner product that allows length and angle to be measured.

32. Technologies researchers are currently employing
Photons
Trapped Atoms
Nuclear Magnetic Resonance
Quantum Dots and dopants in solids
Superconductors
Other Technologies

33. Photons Photonic quantum circuit
Green lines show optical waveguides; yellow components are metallic contacts.
Photons are relatively free of the decoherence
Allow the encoding of a qubit on the basis of location and timing; quantum information may also be encoded in the continuous phase and amplitude variables of many-photon laser beams.
Research Focus: High efficiency single-photon detectors and sources, devices that would enable a deterministic interaction between photons, and chip-scale waveguide quantum circuits.

34. Trapped atoms
The best time and frequency standards are based on isolated atomic systems.
The energy levels in trapped atoms form very reliable qubits, with T1 and T2 times typically in the range of seconds and longer.
Individual atomic ions can be confined in free space with nanometer precision using
appropriate electric fields from
nearby electrodes
Multi-level linear ion trap chip; the inset displays a linear crystal of several ions fluorescing when resonant laser light is applied
(the ion–ion spacing is 4 mm in the figure).

35. Neutral atoms
An array of cold neutral atoms may be confined in free space by a pattern of crossed laser beams, forming an optical lattice
Adjacent atoms can be brought together depending on their internal qubit levels with appropriate laser forces, and through contact interactions.
Schematic of optical lattice of cold atoms formed by multi-dimensional optical standing wave potentials (J. V. Porto).
Image of individual Rb atoms confined in a two-dimensional optical lattice, with atom–atom spacing of 0.64 mm (M. Greiner).

36. Nuclear Magnetic Resonance (NMR)
Nuclear spins in molecules in liquid solutions
Rapid molecular motion helps nuclei maintain their spin orientation for T2 times of many seconds.
Immersed in a strong magnetic field, nuclear spins can be identified.
Irradiating the nuclei with resonant radio-frequency pulses allows manipulation of nuclei of a distinct frequency, giving generic one-qubit gates.
Two-qubit interactions arise from the indirect coupling mediated through molecular electrons.

37. Nuclear Spin
A nucleus with an odd atomic number or an odd mass number has a nuclear spin.
The spinning charged nucleus generates a magnetic field.
=>

38. Two Energy States
The magnetic fields of the spinning nuclei will align either with the external field, or against the field.
A photon with the right amount of energy can be absorbed and cause the spinning proton to flip.

39. NMR spectrometry
A 900MHz NMR instrument with a 21.2 T magnet at HWB-NMR, Birmingham, UK
Chapter 13, Nuclear Magnetic Resonance Spectroscopy Organic Chemistry, 5th Edition L. G. Wade, Jr.

40. Quantum dots and dopants in solids
Motivation: A complication of using single atoms in vacuum is the need to cool and trap them. Need to be integrated into a solid-state host.
Problem: Self-assembled dots are randomly located their optical characteristics vary from dot to dot.
Rapid optical initialization has been demonstrated for both electrons and holes.
Qubits may be controlled very quickly, on the order of picoseconds, potentially enabling extremely fast quantum computers.

41. Electrostatically defined quantum dots, where the confinement is created by controlled voltages on lithographically defined metallic gates. Operate at very low temperatures (~1K) and are primarily controlled electrically,
Self-assembled quantum dots, a random semiconductor growth process creates the potential for confining electrons or holes. operate at higher temperatures (~4 K) and are primarily controlled optically.

42. Optically active solid-state dopants
The atomic structure of a nitrogen-vacancy centre in the diamond lattice, with lattice constant 3.6A Å.
The negatively charged state of the nitrogen vacancy centre forms a triplet spin system.
Under optical illumination, spin-selective relaxations facilitate efficient optical pumping of the system into a single spin state, allowing fast (250 ns) initialization of the spin qubit.
The spin state of a N-vacancy centre may then be coherently manipulated with resonant microwave fields, and then detected in a few milliseconds via spin-dependent fluorescence in an optical microscope
Optically active solid-state dopants also allow photonic connections,
but with greater optical homogeneity. The negatively charged
nitrogen-vacancy centre in diamond (Fig. 4c) is one such dopant. It
consists of a substitutional nitrogen at a lattice site neighbouring a
missing carbon atom. The negatively charged state of the nitrogenvacancy
centre forms a triplet spin system. Under optical illumination,
spin-selective relaxations facilitate efficient optical pumping of
the system into a single spin state, allowing fast (250 ns) initialization
of the spin qubit. The spin state of a nitrogen-vacancy centre may
then be coherently manipulated with resonant microwave fields,
and then detected in a few milliseconds via spin-dependentfluorescence in an optical microscope

43. Arrays of electrostatically defined dots
Each containing a single electron whose two spin states provide a qubit
Quantum logic would be accomplished by changing voltages on the electrostatic gates to move electrons closer and further from each other, activating and deactivating the exchange interaction
The single-electron transistor or quantum point contact allows the measurement of a single electron charge
The control of individual spins has also been demonstrated via direct generation of microwave magnetic and electric fields.

44. Other technologies
The carbon-based nanomaterials of fullerenes, nanotubes and graphene have excellent properties for hosting arrays of electron-based qubits.
Electrons for quantum computing may also be held in a low-decoherence environment on the surface of liquid helium, or be contained in molecular magnets
Schematic diagram of a graphene double quantum dot. Each dot is assumed to have length L and width W. The structure is based on a ribbon of graphene (grey) with semiconducting armchair edges (white).
Trauzettel, B., Bulaev, D. V., Loss, D. & Burkard, G. Spin qubits in graphene quantum dots. Nature Phys. 3, 192–196 (2007).

45. Comparing coherence times:

46. Status of QC Rudimentary Quantum Computers exist
December 19, 2001 – IBM performs Shor’s Algorithm
Quantum computing is so complex that expanding on simple operations is still 10 –20 years away.
Most well known QC’s based on nuclear magnetic resonance (NMR).

47. Future Work Promising techniques for improving coherence times
The central challenge in actually building quantum computers is maintaining the simultaneous abilities to control quantum systems, to measure them, and to preserve their strong isolation from uncontrolled parts of their environment.

48. Questions? Thanks 4/1/2017 6:27 AM
© 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

49. G5 Rebuttal: Quantum mechanical devices
Norma L. Rangel

50. Norma Rangel – Rebuttal
The featured paper (review) was very recent and potentially interesting to the audience. Although a bit unorganized, the slides had a fair amount of information and graphics. However, some references were missing or incomplete
Certainly, there were not references in every slide, but somewhere all the sources were cited in the ppt.
I know the topic was hard, but the speaker constantly apologized instead of focusing on giving her best effort, projecting confidence and credibility. The speaker gave the impression of not having a good enough knowledge of the basic theory behind the presented technology, although might rather be lack of confidence handling this specific topic.
I apologize (again) for my lack of confidence, certainly more time was require from myself to successfully cover this topic since it was not in my confidence field.
A friendlier outline of the presentation would have helped a lot. The sequence of slides was not optimal. For instance, after three slides talking about SET, there was one slide with the schematics of quantum tunneling, where actually the instructor had to intervene to explain it. It would have been better start with slide explaining quantum tunneling , and then follow with the device that uses that principle.
I fully agree with the reviewer, an outline could have been very helpful but I didn’t use it because I tried to cover two main topics: SET and QC, most of the remaining the topics came out from definitions that I found appropiate to help the audience understand the lecture.

51. Generally, the subject was presented with ease of understanding, as this topic can be very hard to understand. However, this led to somewhat lacking depth in the subject.
I tried to made the presentation somehow helpful to undergrads (majority in the audience) to understand, since a very technical background was needed to follow the topic.
The connection between the introduction (SET) and the reviewed paper (Quantum Computer) was weak, interrupting the flow of the presentation. Choosing a paper with applications using SET might better induce the flow of the overall presentation.
I agree with the reviewer, I think the connection between the SET and the quantum computer hardware was lost, my intension of having SETs as an introduction of QCs was because SETs are one of the components of a QC, however I know realize that an introduction only based on concepts could have been more helpful. Also, I believe that since I wanted to define most of the concepts needed for the presentation made the connection between the two components.

52. G1 Review: Quantum mechanical devices
Edson Bellido

53. The presenter explained how the BJT and FET transistors work
The presenter explained how the BJT and FET transistors work. She explained what a tunnel junction, quantum tunneling, coulomb island and coulomb blockade are. This concepts help to understand how a SET works.
She gave an example of SET using graphene where they have analyzed the conductance of a device with the central island as a function of Vg in the vicinity.
Tunneling
The presenter also introduced the concept of quantum computer as well as a comparison between a traditional bit and a qubit. She explain some of the features and potential applications of the quantum computer.
She stated the some criteria we have to consider to implement a quantum computer these are: scalability, initialization, control, stability, measurement. Also the physical requirements which are that the computer must operate in a Hilbert space, the space must be accessible using a finite set of control operations and it must be possible to extract the entropy of the computer to maintain the computer’s quantum state.

54. It was also presented the technologies that are currently use to test the concepts of quantum computing and implement some prototypes. They are using photons, trapped atoms, nuclear magnetic resonance, quantum dots and dopants in solids and superconductors. She explained how researchers are using these technology to fabricate quantum computers and gave some experimental examples.
The overall presentation was informative. However, I think that it would be more interesting if instead of a very shallow overview of quantum computing the presenter would have explain just one application or one device in detail. Some of the concepts were not well explained but this understandable due to the complexity of the topic.
Personally I find this topic very interesting specially because there is many things we do not fully understand, for example: why there is quantum entanglement?.

55. G2 Review: Quantum mechanical devices
Alfredo Bobadilla

56. Single Electron Transistor Lecture Review
Problems related with integration of single electron transistors (SET) in molecular circuits were not analyzed. These include the diffraction limit in optical lithography and the increase in thermal noise when integrating a much higher number of transistors. And it was not shown where SET research stands currently, what is needed or what is being tried to make this commercially available.
Concepts related to quantum physics were not correctly clarified. The key idea was not simplified, i.e. how quantum phenomena is aimed to be used in quantum computer. I think some physics terminology (Hilbert’s space, decoherence time, etc) could have been explained in more friendly terms. Other fundamental physics concepts like qubits and entanglement needed a deeper analysis.
Alfredo D. Bobadilla

57. Single Electron Transistor Lecture Review
The analysis of quantum computers was broad, being considered not only advantages but also disadvantages. Nevertheless suggestions were not given to further advance the area. The inherent problem is the environment perturbing the quantum states of the system. Other problems are the high cost and the complex fabrication process implied on the current alternatives for a quantum computer. I would suggest looking for a solution in biological systems. Biological phenomena such as photosynthesis is based on quantum effects (doi: /nature05678), and it seems the lipid bilayer is a good isolator from the environment. It has already been shown recently hybrid nanostructures with lipid layer covering tubular nanostructures such as microtubules (doi: /pnas ), carbon nanotubes (pubs.acs.org/doi/abs/ /nl100499x) and silicon nanowires (doi: /pnas ).
Alfredo D. Bobadilla

58. Review of Quantum Devices Norma Rangel’s Presentation
By Mary Coan G3

59. Review Discussed the basics of Transistors
BJTs, FETs, SETs
Described the following in a fundamental way
tunneling/tunnel junctions
Coulomb blockade
Good for those who have not experienced this information before
Linked background information to the topic of the presentation in an organized manner
Gave examples of SETs
Fabrication methods
Graphene SET

60. Review Reviewed Quantum Computers (QCs) Defined Quantum Computers
Light to laser
Bit to Qubit
Examples of technologies for QCs
Implementation of QCs
Scalability
Initialization
Control
Measurement
Decoherence

61. Review Discussed current technologies researchers are employing
Current Status of QCs
Future Work was also discussed
Overall the presentation was put together very well
Supplied information in a organized manner
Presentation was geared towards the majority of the class, undergraduates
This is appropriate
Used graphics to describe information and equations
Very helpful

62. G4 Review (Quantum Devices)
Diego A Gómez-Gualdrón

63. A Tunnel Junction
A thin layer of insulator separating two electrodes is know as ‘Tunnel Junction’
Physics of the Junction
Schematics of Tunnel Junction
Classical mechanics says no electron can flow through the insulating barrier
Quantum mechanics says one electron can flow through the barrier by ‘tunneling’
electrode
electrode V1 V2
The barrier as a resistor
The larger the bias voltage V1-V2, the more frequent the pass of electrons
Insulator
The thicker the barrier, the more resistant
The insulator barrier also has a finite capacitance C. When an electron tunnels, there is a voltage build up according to V= e/C

64. V= e/C Coulomb Blockade
The increase of the (differential) resistance at low bias in a Tunnel Junction is known a ‘Coulomb Blockade’
Schematics of Coulomb Blockade
Conditions
electrons
electrode 1)
Extremely low capacitance of the junction
Low bias between electrodes
Low thermal energy of the electrons 2)
V= e/C 3)
If the C is low enough, then the entrance of just one electron (e) rises V so much as to refrain more electrons from passing

65. Single Electron Transistor
They take advantage of the coulomb blockade effect to control the ‘current’ of electrons, and are composed by two tunnel junctions sharing a common electrode
Schematics of SET
How
drain
source
The common electrode is called ‘island’
The voltage of the gate affects the energy levels of the island
electrode
common electrode
electrode V1 V2 V1
One source electron tunnels through the island
Coulomb blockade occurs until the electron tunnels to the drain
Insulator
Insulator
Gate

66. A qubit made out two states
Quantum Computing
A different kind of computers taking advantage of quantum entanglement of particles
The Bloch sphere
Uses qubits
A qubit made out two states
A qubit is a quantum state
The total quantum state is a linear combination of particles states
The state of each particle is represented by kets such as |0 > and |1>
Instead of using 8 bits (0’s and 1’s)to represent uses one qubit {|0 > + |1> + |0 > + |0 > + |1> + |1> + |1> + |0 > }

67. REVIEW
The presentation was given in two parts: the first one, the description, working principle and fabrication of single electron transistors; the second one, a review in the nascent area of quantum computing
The featured paper (review) was very recent and potentially interesting to the audience. Although a bit unorganized, the slides had a fair amount of information and graphics. However, some references were missing or incomplete

68. REVIEW
I know the topic was hard, but the speaker constantly apologized instead of focusing on giving her best effort, projecting confidence and credibility
The speaker gave the impression of not having a good enough knowledge of the basic theory behind the presented technology, although might rather be lack of confidence handling this specific topic

69. REVIEW
A friendlier outline of the presentation would have helped a lot. The sequence of slides was not optimal. For instance, after three slides talking about SET, there was one slide with the schematics of quantum tunneling, where actually the instructor had to intervene to explain it. It would have been better start with slide explaining quantum tunneling , and then follow with the device that uses that principle.

70. Review for G5
Jung Hwan Woo

71. Generally, the subject was presented with ease of understanding, as this topic can be very hard to understand. However, this led to somewhat lacking depth in the subject.
The connection between the introduction (SET) and the reviewed paper (Quantum Computer) was weak, interrupting the flow of the presentation. Choosing a paper with applications using SET might better induce the flow of the overall presentation.