Free Will and Retrocausality in the Quantum World
A conference held under the auspices of the JTF-funded
project, New
Agendas for the Study of Time
Venue: Winstanley Lecture Theatre, Trinity
College, Cambridge
Dates: 1—4 July 2014
Programme [with links to videos of talks and discussion sessions]
Why retrocausality — and why free will?
The 'classic' motivation for retrocausal models in QM
stems from Bell's Theorem, and the nonlocality it seems
to entail. Nonlocality is often felt to be
counterintuitive in itself, and the source of an
unresolved tension between quantum theory and special
relativity. As Bell himself described the implications
of his famous result: “[I]t's a deep dilemma, and the
resolution of it will not be trivial ... [T]he cheapest
resolution is something like going back to relativity as
it was before Einstein, when people like Lorentz and
Poincaré thought
that there was an aether — a preferred frame of
reference — but that our measuring instruments were
distorted by motion in such a way that we could not
detect motion through the aether.''
As Bell was well aware, the dilemma can be avoided if
the properties of quantum systems are allowed to depend
on what happens to them in the future, as well
as in the past. Like most researchers interested in
these issues, however, Bell felt that the cure would be
worse than the disease — he thought that this kind of
“retrocausality” would conflict with free will, and with
assumptions fundamental to the practice of science. (He
said that when he tried to think about retrocausality,
he “lapsed into fatalism”.)
If this objection to retrocausality in QM is
well-founded, it raises interesting issues about the
nature and origins of this "free will", that turns out
to play such a surprising role in the foundations of
physics. If the objection is not well-founded, then it
is high time it is moved aside, so that the retrocausal
approach can be given the attention it otherwise seems
to deserve.
Moreover, there are other motivations for exploring
retrocausal models in QM, some the focus of considerable
current research. Examples include:
- The proposed retrocausal explanation of the results
of 'weak measurements' by Aharonov, Vaidman and
others.
- The relevance of retrocausality to the issue of the
viability of an 'epistemic' interpretation of the
quantum state, especially in the light of recent
results such as the PBR Theorem.
- Recent work throwing new
light on the relation between retrocausality in QM,
on the one hand, and time-symmetry and other
symmetries, on the other.
For these reasons, too, there is a pressing need for a
better understanding of notions of free will and
causality, and of their relevance to the retrocausal
approach to the quantum world. This conference brought together many of the leading writers and
researchers on these topics, to discuss these issues.
Participants and invitees:
John-Mark Allen, Jonathan Barrett, Howard Barnum, Stephen Bartlett, Dan
Bedingham, Gordon Belot, David Braddon-Mitchell, Jeremy Butterfield,
Adam Caulton, Eliahu Cohen, Karen Crowther, Phil Dowe, Fay Dowker,
Avshalom Elitzur, Matt Farr, Nicolas Gisin, Berry Groisman, Joe Henson,
Jenann Ismael, Ruth Kastner, Adrian Kent, James Ladyman, Ray Lal,
Dustin Lazarovici, Ciaran Lee, Matt Leifer, Peter Lewis, Owen Maroney,
Joseph Melia, Sonny Mendez, David Miller, Kristie Miller, Nick Murphy,
Tim Palmer, Brian Pitts, Sandu Popescu, Huw Price, Matt Pusey, Dean
Rickles, Sebastian Rivat, Bryan Roberts, Terry Rudolph, Rafael Sorkin,
Nick Teh, Chris Timpson, Jeff Tollaksen, James Troupe, Lev Vaidman, Ken
Wharton, Steve Weinstein, Lena Zuchowski.
Organisers: Huw
Price (Philosophy and Trinity College, Cambridge)
and Matt Farr
(Centre
for Time, Sydney)
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