Superconducting Qubits
Introduction and Background
The quantum computation has remarkably improved since the use of quan-
tum algorithms that have a run time which is exponentially faster compared
to classical algorithms. Implementation of theory for practical computation
presents various technological and scientific challenges. It is required that
the Qubits be entirely free from external noise while at the same time they
need to be strongly coupled amongst themselves using gates for computa-
tion.
We need to construct the qubits such that their degrees of freedom are
independent of the noise in the environment. For example electronic spins
or spins of nuclei are isolated from surrounding noise. In superconduct-
ing qubits we see a macroscopic quantum system. It is constructed using
macroscopic electrical elements such as inductors and capacitors that can
be coupled owing to their considerably large electromagnetic interaction
areas. Over the years the goal has remained to isolate the systems from
background noise as well as maintaining controlling, writing and reading
operations which are done using external signals.
We use Quantum integrated circuits which have least dissipation such
that metallic parts are in superconducting state which have zero resistance.
Also when the system is in ultra low temperatures it ensures that thermal
energy (kT ) is very less than energy ( ̄ ω01 ) needed for the transition of
h
qubits from |0 state to |1 state. The temperature required are nearly as
1
2
CHAPTER 1. SUPERCONDUCTING QUBITS
low as 20mK and transition frequencies are in the range of 5 − 20GHz. We
need ̄ ω01 < ∆ and kT < ̄ ω01 (∆ is the superconducting energy gap).
h
h
1.1.1
Macroscopic quantum syste...
... middle of paper ...
... critical current. The Cooper pair box acquires non-linearity at the
expense of its sensitivity to of set charge noise. The search for the optimal
qubit circuit involves therefore a detailed knowledge of the relative intensities
of the various sources of noise, and their variations with all the construction
parameters of the qubit.
Bibliography
[1] Superconducting Qubits: A Short Review M. H. Devorety, A. Wallrafy,
and J. M. Martinis yDepartment of Applied Physics, Yale University,
New Haven, CT 06520 Department of Physics, University of California,
Santa Barbara, CA 93106 October 11, 2004
[2] Quantum computation with superconducting qubits. Ognjen Malkoc
June 10, 2013
[3] Superconducting Qubits and the Physics of Josephson Junctions John
M. Martinis and Kevin Osborne
[4] Neilson and Chuang, Quantum Computation and Quantum Informa-
tion ........
11
How do you view the use of public funds to support certain activities in church schools? Do you see a trend toward “excessive entanglement”? Where do you see the line needing to be drawn so as not to conflict with the establishment clause?
Giuseppe Cocconi and Philip Morrison published a paper in Nature in September 1959, in which they suggest a probable frequency at which alien civilizations would attempt to communicate: 1.420 GHz. This is the frequency of electromagnetic radiation emitted by neutral Hydrogen during a change of energy state. The frequency is an important physical and astronomical value, would almost certainly be known by any civilization capable of communication, and it requires only relatively simple technology to broadcast at this frequency. As Cocconi and Morrison put it, “It is reasonable to expect that sensitive receivers for this frequency would be made at an early stage of the development of radioastronomy. That would be the expectation of the operators of the assumed source, and the present state of terrestrial instruments indeed justifies the expectation.” In other words, it makes sense that aliens would come to the same conclusion about the 1.420 GHz frequency. If the aliens want to communicate with us...
The molar specific heats of most solids at room temperature and above are nearly constant, in agreement with the Law of Dulong and Petit. At lower temperatures the specific heats drop as quantum processes become significant. The Einstein-Debye model of specific heat describes the low temperature behavior.
These reactions take place unexpectedly. However, the rate of an unexpected reaction may not be very great. This is because an energy hurdle must first be defeated.
23. S. Alwarappan, S. Boyapalle, A. Kumar, C.-Z. Li and S. Mohapatra, J. Phys. Chem. C, 2012, 116, 6556–6559
1 David Halliday, Robert Resnick, and Jearl Walker, Fundamentals of Physics, Extended, 5th ed. (NewYork:Wiley, 1997) 361
Each atom can exist in an unlimited number of different states, the so-called stationary states. Each of these stationary states is characterized by a given energy level. The difference between two such energy levels, divided by Planck’s constant h, is the oscillation frequency of a spectral line that can be emitted by the atom.
Serway, Raymond A, and Robert J Beichner. Physics: For Scientists and Engineers. United States of
an initial energy of about 1 MeV will induce fission is rather low, but can be
American Institute of Physics. Vol. 1051 Issue 1 (2008). Academic Search Premier.> 224. http://login.ezproxy1.lib.asu.edu/login?url=http://search.ebscohost.com.ezproxy1.lib.asu.edu/login.aspx?direct=true&db=aph&AN=34874307&site=ehost-live.
Condensed Matter Physics, in its early conception, was not known by its more modern terminology but emanated from Solid State Physics. Comparable to Astronomy, Solid State Physics is the oldest subcategory of what we now refer to as Physics. Condensed-matter physics is broader and applies to concepts that work in solids, but could equally be applied to liquids: superconductivity vs. superfluidity, and soft-condensed matter. Condensed Matter Physics has contributed properties of materials including electronic, magnetic, dynamical, mechanical, and thermo-dynamical properties of nanoscale systems and materials such as but not limited to: Metals and alloys, semiconductors, superconductors, polymers, ceramics, crystal, amorphous and cluster-like states. Condensed Matter Physics is interdisciplinary and intertwined with inorganic chemistry, physical chemistry, quantum chemistry, electrical and mechanical. It tries to connect the properties of the nuclei and electrons to the macroscopically observed quantities. As in other fields of study, advancement in condensed matter resulted from impro...
2. A He and H atom collide elastically in a head-on collision. (a). If they have the same kinetic energy (KE) to begin with, which one gains KE? Answer this by calculating the amount gained and lost for both, relative to their initial value. (b). Suppose the atoms had the same mass but different kinetic energies? Do not do a detailed calculation here, but instead make a physical argument as to why the “slower” thus “cooler” atoms would slow down the faster, hotter atoms. This is one process for the moderation of hot neutrons in a nuclear fission reactor by the water used as its coolant.
The development of superconductors has been a working progress for many years and some superconductors are already in use, but there is always room for improvement. In 1911, Dutch physicist Heike Kamerlingh Onnes first discovered superconductivity when he cooled mercury to 4 degrees K (-452.47º F / -269.15º C). At this temperature, mercury’s resistance to electricity seemed to disappear. Hence, it was necessary for Onnes to come within 4 degrees of the coldest temperature that is theoretically attainable to witness the phenomenon of superconductivity. Later, in 1933 Walter Meissner and Robert Ochsenfeld discovered that a superconducting material will repel a magnetic field. A magnet moving by a conductor induces currents in the conductor, which is the principle upon which the electric generator operates. However, in a superconductor the induced currents exactly mirror the field that would have otherwise penetrated the superconducting material - causing the magnet to be repulsed- known today as the “Meissner effect.” The Meissner effect is so strong that a magnet can actually be levitated over a superconductive material, which increases the use of superconductors. After many other superconducting elements, compounds, and theories related to superconductivity were developed or discovered a great breakthrough was made. In 1986, Alex Muller and Georg Bednorz invented a ceramic substance which superconducted at the highest temperature then known: 30 K (-243.15º C). This discovery was remarkable because ceramics are normally insulators – they do not conduct electricity well. Since their discovery the highest temperature for superconductivity to occur is 138 K (-130.15º C).
... S.M., My Yang, Halvorson, D.A & Sreevatsan, S. (2009) The Feasibility of Using High
gigahertz. (1 kilohertz = 1000 hertz : 1 megahertz = 106 hertz, 1 gigahertz =