by Gu Mile
School of
Physical and Mathematical Sciences
Nanyang Technological University
April 09, 2019
from
PHYS Website
Unlike classical particles,
quantum
particles can travel in a
quantum
superposition of different directions.
Mile Gu,
together with researchers from Griffith
harnessed this phenomena to design quantum devices
that
can generate a quantum superposition
of all
possible futures.
Credit:
NTU, Singapore.
In the 2018 movie 'Avengers
 Infinity War,' a scene featured Dr. Strange
looking into 14 million possible futures to search for a
single timeline in which the heroes would be victorious.
Perhaps he would have had
an easier time with help from a
quantum computer.
A team of researchers
from Nanyang Technological University, Singapore (NTU
Singapore) and Griffith University in Australia have constructed a
prototype quantum device that can generate all possible
futures in a simultaneous quantum superposition.
"When we think about
the future, we are confronted by a vast array of possibilities,"
explains Assistant Professor Mile Gu of NTU Singapore, who led
development of the quantum algorithm that underpins the
prototype.
"These possibilities
grow exponentially as we go deeper into the future.
For instance, even if
we have only two possibilities to choose from each minute, in
less than half an hour there are 14 million possible futures.
In less than a day,
the number exceeds the number of atoms in the universe."
What he and his research
group realized, however, was that a quantum computer can examine all
possible futures by placing them in a
quantum superposition  similar to
Schrödinger's famous cat, which is
simultaneously alive and dead.
To realize this scheme, they joined forces with the experimental
group led by Professor Geoff Pryde at Griffith University.
Together, the team
implemented a specially devised photonic quantum information
processor in which the potential future outcomes of a decision
process are represented by the locations of photons  quantum
particles of light.
They then demonstrated
that the state of the quantum device was a superposition of multiple
potential futures, weighted by their probability of occurrence.
A picture of the Experimental Device
used
for the experiment.
Credit:
Griffith’s University
"The functioning of
this device is inspired by the Nobel Laureate Richard Feynman,"
says Dr. Jayne Thompson, a member of the Singapore team.
"When Feynman started
studying quantum physics, he realized that when a particle
travels from point A to point B, it does not necessarily follow
a single path. Instead, it simultaneously transverses all
possible paths connecting the points.
Our work extends this
phenomenon and harnesses it for modeling statistical futures."
The machine has already
demonstrated one application  measuring how much our bias towards a
specific choice in the present impacts the future.
"Our approach is to
synthesize a quantum superposition of all possible futures for
each bias." explains Farzad Ghafari, a member of the
experimental team.
"By interfering these
superpositions with each other, we can completely avoid looking
at each possible future individually.
In fact, many current
artificial intelligence (AI)
algorithms learn by seeing how small changes in their behavior
can lead to different future outcomes, so our techniques may
enable quantum enhanced AIs to learn the effect of their actions
much more efficiently."
The team notes while
their present prototype simulates at most 16 futures
simultaneously, the underlying quantum algorithm can in
principle scale without bound.
"This is what makes
the field so exciting," says Pryde.
"It is very much
reminiscent of classical computers in the 1960s. Just as few
could imagine the many uses of classical computers in the 1960s,
we are still very much in the dark about what quantum computers
can do.
Each discovery of a
new application provides further impetus for their technological
development."
The work (Interfering
Trajectories in Experimental QuantumEnhanced Stochastic Simulation)
is featured in a forthcoming paper in the journal Nature
Communications.
