Main ideas of a NMR quantum computer. Advantages of NMR. Nucleus is naturally protected from outside interference. Once the spins are lined up they will stay in the proper order for a long time. Nuclear qubits already exist in nature.
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1Liquid State NMR Ensemble Computers
Many molecules (e..g, 1018) can be combined in liquid solution to form a same-state ensemble of macroscopic and manageable size
All of Di Vicenzo’s criteria can be met, except that scalability seems to be limited to 20–30 qubits?
The spins remain selectively addressable due to different resonant frequencies
Illustrative Example of radio frequencies (RF) interacting with spin.
An RF pulse can rotate an atom’s spin in a manner proportional to the amplitudeand duration of the applied pulse
Most NMR applications treat spins as little "bar magnets", whereas in reality, the naturally well-isolated nuclei are non-classical objects.
Static field coil
Quantum computing researchers: (l-r) Isaac Chuang and Costantino Yannoni
Diagram of the 7-qubit molecule
Alanine, an amino acid.
From IBM research news
M. Steffen1,2, L.M.K. Vandersypen1,2, G. Breyta1,
C.S. Yannoni1, M. Sherwood1, I.L.Chuang1,3
1 IBM Almaden Research Center, San Jose, CA 95120
2 Stanford University, Stanford, CA 94305
3 MIT Media Laboratory, Cambridge, MA 02139
‡Vandersypen L.M.K, et al, Nature, v.414, pp. 883 – 887 (2001)
Quantum circuit to factor an integer N
Implemented for the case N = 15 -- expect 3 and 5
a = 7
a = 11
~ 300 RF pulses || ~ 750 ms duration
Mixture of |0,|4
23/4 = r = 2
gcd(112/2 ± 1, 15) = 3, 5
a = 11
15 = 3 · 5
a = 7
Mixture of |0,|2,|4,|6
23/2 = r = 4
gcd(74/2 ± 1, 15) = 3, 5