16 | New Scientist | 8 February 2020
A NEW method for manipulating the
quantum state of particles has been
used to chill a tiny glass bead into
its coldest possible quantum state.
Once you get down to extremely
small scales, heat and motion are
interchangeable: the more a particle
is moving, the hotter it is. So to cool
down a small particle, you have to
stop it moving. Because the rules
of quantum mechanics mean you
can never know exactly how fast
a particle is moving, there is a limit
to how cold a particle can get. When
a particle is at that limit, we say
it has reached its ground state.
Markus Aspelmeyer at the
University of Vienna in Austria and
his colleagues used a single laser
to cool a 150-nanometre-wide
glass particle into its ground state
The laser levitated the particle
through an effect called optical
trapping, in which the light
interacted with the particle to hold
it in place. Mirrors either side of the
particle caused the light to overlap
and interfere with itself.
This interfering light could
only exist in certain frequencies,
according to quantum mechanics.
That allowed the researchers to
select the precise frequencies of
light that hit the particle. As the
particle vibrated back and forth,
some frequencies of light would
have sped it up by imparting small
amounts of energy, while others
would have slowed it down by
Allowing only the frequencies
that slowed the particle meant
it kept cooling until it reached its
ground state. This occurred at a
temperature of 0.000012 kelvin
(about -273°C), just a fraction
above absolute zero, the minimum
temperature possible. ❚
ARTIFICIAL intelligence is helping
to select embryos for IVF that
have a higher chance of resulting
in a successful pregnancy.
The AI algorithm, called Ivy,
analyses time-lapse videos of
embryos as they are incubated
after being fertilised, and
identifies which ones have the
highest likelihood of success.
It was developed by Harrison.ai,
a tech firm in Sydney, and has been
used for several thousand women
undergoing IVF in Australia.
People who undergo IVF using
Ivy are informed about the
algorithm and consent to its use.
Ivy was trained on more than
10,000 videos of embryos growing
inside an incubator for five days,
in combination with data about
which embryos resulted in
pregnancy. The model is more
accurate than trained specialists
at predicting the likelihood that
an embryo will go on to develop
a fetal heartbeat at or beyond
seven weeks of gestation.
In a study of its predictive
ability, Ivy scored 0.93 on a
measure known as AUC, where
a score of 1 indicates a model
with predictions that are 100 per
cent correct. Trained human
embryologists have previously
scored an AUC of around 0.74.
“The results look very
promising,” says Iman
Hajirasouliha at Cornell University
in New York. He and his colleagues
have developed a similar AI, Stork.
What these AIs are identifying
in the videos as a marker of
success isn’t entirely clear.
“It’s still a bit of a black box,” says
Aengus Tran, CEO of Harrison.ai.
“We could speculate that it must
have learned very similar features
to what embryologists are looking
at,” says Tran. These might include
the shape of cells or how long it
takes to go from two to eight cells.
Ivy may also have picked up
on features that human specialists
don’t look at, says Tran. While
embryologists look only at video
snippets of key events of an
embryo’s development, Ivy
is able to rapidly analyse the
entirety of five days of footage.
Ivy is now routinely used as a
tool in embryo selection by IVF
Australia, which provides about
20 per cent of the country’s IVF
services. “Because we think
it’s a better predictor than
the embryologists, we are
choosing the embryos with
Ivy most of the time,” says Peter
Illingworth at IVF Australia.
A clinical trial will begin next
month to determine whether
people undergoing IVF whose
embryos are selected by Ivy
become pregnant more quickly
than those whose embryos are
selected by human specialists.
In an average IVF cycle, a parent
starts with 10 eggs that result in
three potentially viable fertilised
embryos after five days, says
Illingworth. One is implanted,
and the rest are frozen and stored.
“Ultimately, what you really
want is one IVF cycle resulting
in one embryo being transferred
and one healthy baby,” says Tran.
“What we’re not doing is
using Ivy to decide which
embryos we will freeze and
keep,” says Illingworth. “Ivy
will never make the difference
between a woman having a
baby or not having a baby.” ❚
Eggs undergoing IVF have
different probabilities of
developing into embryos
Temperature the nanoparticle
was cooled to
quantum chilled to
near absolute zero
AI attempts to pick embryos with
the best chance of IVF success