Quantum Control

• Quantum compiling• Algorithms as closed

loop control circuits• Correcting quantum

errors with unitary operations

Shaped Ultrafast Optical Pumping of NMR

Systems

Jason Taylor / Neil Gershenfeld

MIT Media Lab

Daniel Morris / Phil Bucksbaum

University of Michigan

Typical pulse shaper with feedback

goals

• Increase nuclear polarization– Unity polarization would be nice for quantum

computers

• Decrease nuclear polarization– Resetting qubits is necessary for quantum error

correction

• Selectively polarize nuclei

NMR & Biology

• Tools for accessible NMR– Table-top NMR (whole systems, amplifiers)– Automatic shimming

• Ultimate goal:– Biological structure via NMR

• Imaging

• Structure calculations

• ??

Radio Frequency Graphical Models Implemented in Analog

Circuits

Benjamin Vigoda

MIT Media Lab

A Spread Spectrum Radio System

AFSR Iterative Factor GraphFinds phase of 4 bin, 2 tap LFSR

Soft Gates for Coding

pz(1) = px(1) py(1)

pz(0) = px(0) py(0)

pz(1) = px(0) py(1) + px(1) py(0)

pz(0) = px(0) py(0) + px(1) py(1)

For Binary Symmetric Channel with Hard Decision

pz(x=1|y = 0) = p(x=0|y=1) = 1-A

pz(x=1|y = 1) = p(x=0|y=0) = A

Translinear Multiplier SoftGateSource Referenced Subthreshold MOSFET:

IDS = IO e KSVGS /t (1 – e -VDS /t ) For understanding circuit, think:

IDS = IO e KVGS

Circuit Computes:

pz(1) = px(0) py(1) + px(1) py(0)

pz(0) = px(0) py(0) + px(1) py(1)