Roope Uola

PhD student
Room: B-106
Phone: +49 271 740 3774
roope.uola@gmail.comPreprints
See also arxiv
Roope Uola, Tristan Kraft, Jiangwei Shang, Xiao-Dong Yu and Otfried Gühne
Quantifying quantum resources with conic programming
arXiv:1812.09216
Resource theories can be used to formalize the quantification and
manipulation of resources in quantum information processing such as
entanglement, asymmetry and coherence of quantum states, and incompatibility of
quantum measurements. Given a certain state or measurement, one can ask whether
there is a task in which it performs better than any resourceless state or
measurement. Using conic programming, we prove that any general robustness
measure (with respect to a convex set of free states or measurements) can be
seen as a quantifier of such outperformance in some discrimination task. We
apply the technique to various examples, e.g. joint measurability, POVMs
simulable by projective measurements, and state assemblages preparable with a
given Schmidt number.
Roope Uola, Giuseppe Vitagliano and Costantino Budroni
Leggett-Garg macrorealism and the quantum nondisturbance conditions
arXiv:1812.02346
We investigate the relation between a refined version of Leggett and Garg
conditions for macrorealism, namely the no-signaling-in-time (NSIT) conditions,
and the quantum mechanical notion of nondisturbance, and obtain a compatibility
relation among an arbitrary number of observables based on their minimally
disturbing sequential implementation. We show that all NSIT conditions are
satisfied for any state preparation if and only if simple compatibility
criteria on the state-update rules relative to the observables, i.e. quantum
instruments, are met. Motivated by this connection, we prove some structural
results on nondisturbance of two or more observables, such as the existence of
noncommuting and two-way nondisturbing observables, and pairwise but not
triplewise nondisturbing observables. Moreover, we discuss perspectives for a
resource theory of quantum disturbance based on the notion of macrorealism by
defining a general measure of disturbance and investigating which operations do
not increase it.
Publications
Ana C. S. Costa, Roope Uola and Otfried Gühne
Entropic Steering Criteria: Applications to Bipartite and Tripartite
Systems
Entropy 20,
763
(2018),
arXiv:1808.01198
The effect of quantum steering describes a possible action at a distance via
local measurements. Whereas many attempts on characterizing steerability have
been pursued, answering the question as to whether a given state is steerable
or not remains a difficult task. Here, we investigate the applicability of a
recently proposed method for building steering criteria from generalized
entropic uncertainty relations. This method works for any entropy which satisfy
the properties of (i) (pseudo-) additivity for independent distributions; (ii)
state independent entropic uncertainty relation (EUR); and (iii) joint
convexity of a corresponding relative entropy. Our study extends the former
analysis to Tsallis and R\'enyi entropies on bipartite and tripartite systems.
As examples, we investigate the steerability of the three-qubit GHZ and W
states.
Ana C. S. Costa, Roope Uola and Otfried Gühne
Steering criteria from general entropic uncertainty relations
Phys. Rev. A 98,
050104
(2018),
arXiv:1710.04541
The effect of steering describes a possible action at a distance via
measurements but characterizing the quantum states that can be used for this
task remains difficult. We provide a method to derive sufficient criteria for
steering from entropic uncertainty relations using generalized entropies. We
demonstrate that the resulting criteria outperform existing criteria in several
scenarios; moreover, they allow one to detect weakly steerable states.
Roope Uola, Fabiano Lever, Otfried Gühne and Juha-Pekka Pellonpää
Unified picture for spatial, temporal and channel steering
Phys. Rev. A 97,
032301
(2018),
arXiv:1707.09237
Quantum steering describes how local actions on a quantum system can affect
another, space-like separated, quantum state. Lately, quantum steering has been
formulated also for time-like scenarios and for quantum channels. We approach
all the three scenarios as one using tools from Stinespring dilations of
quantum channels. By applying our technique we link all three steering problems
one-to-one with the incompatibility of quantum measurements, a result formerly
known only for spatial steering. We exploit this connection by showing how
measurement uncertainty relations can be used as tight steering inequalities
for all three scenarios. Moreover, we show that certain notions of temporal and
spatial steering are fully equivalent and prove a hierarchy between temporal
steering and macrorealistic hidden variable models.
Jukka Kiukas, Costantino Budroni, Roope Uola and Juha-Pekka Pellonpää
Continuous variable steering and incompatibility via state-channel
duality
Phys. Rev. A 96,
042331
(2017),
arXiv:1704.05734
The term Einstein-Podolsky-Rosen steering refers to a quantum correlation
intermediate between entanglement and Bell nonlocality, which has been
connected to another fundamental quantum property: measurement incompatibility.
In the finite-dimensional case, efficient computational methods to quantify
steerability have been developed. In the infinite-dimensional case, however,
less theoretical tools are available. Here, we approach the problem of
steerability in the continuous variable case via a notion of state-channel
correspondence, which generalizes the well-known Choi-Jamio\l{}kowski
correspondence. Via our approach we are able to generalize the connection
between steering and incompatibility to the continuous variable case and to
connect the steerability of a state with the incompatibility breaking property
of a quantum channel, e.g., noisy NOON states and amplitude damping channels.
Moreover, we apply our methods to the Gaussian steering setting, proving, among
other things, that canonical quadratures are sufficient for steering Gaussian
states.
Roope Uola, Kimmo Luoma, Tobias Moroder and Teiko Heinosaari
Adaptive strategy for joint measurements
Phys. Rev. A 94,
022109
(2016),
arXiv:1604.08724
We develop a technique to find simultaneous measurements for noisy quantum
observables in finite-dimensional Hilbert spaces. We use the method to derive
lower bounds for the noise needed to make incompatible measurements jointly
measurable. Using our strategy together with recent devel- opments in the field
of one-sided quantum information processing we show that the attained lower
bounds are tight for various symmetric sets of quantum measurements. We use
this characterisation to prove the existence of so called 4-Specker sets in the
qubit case.
Tobias Moroder, Oleg Gittsovich, Marcus Huber, Roope Uola and Otfried Gühne
Steering maps and their application to dimension-bounded steering
Phys. Rev. Lett. 116,
090403
(2016),
arXiv:1412.2623
The existence of quantum correlations that allow one party to steer the
quantum state of another party is a counterintuitive quantum effect that has
been described already at the beginning of the past century. Steering occurs if
entanglement can be proven although the description of the measurements on one
party is not known, while the other side is characterized. We introduce the
concept of steering maps that allow to unlock the sophisticated techniques
developed in regular entanglement detection to be used for certifying
steerability. As an application we show that this allows to go even beyond the
canonical steering scenario, enabling a generalized dimension-bounded steering
where one only assumes the Hilbert space dimension on the characterized side,
but no description of the measurements. Surprisingly this does not weaken the
detection strength of very symmetric scenarios that have recently been carried
out in experiments.
Roope Uola, Costantino Budroni, Otfried Gühne and Juha-Pekka Pellonpää
One-to-one mapping between steering and joint measurability problems
Phys. Rev. Lett. 115,
230402
(2015),
arXiv:1507.08633
Quantum steering refers to the possibility for Alice to remotely steer Bob's
state by performing local measurements on her half of a bipartite system. Two
necessary ingredients for steering are entanglement and incompatibility of
Alice's measurements. In particular, it has been recently proven that for the
case of pure states of maximal Schmidt rank the problem of steerability for
Bob's assemblage is equivalent to the problem of joint measurability for
Alice's observables. We show that such an equivalence holds in general, namely,
the steerability of any assemblage can always be formulated as a joint
measurability problem, and vice versa. We use this connection to introduce
steering inequalities from joint measurability criteria and develop quantifiers
for the incompatibility of measurements.
Erkka Haapasalo, Juha-Pekka Pellonpää and Roope Uola
Compatibility properties of extreme quantum observables
Lett. Math. Phys. 105,
661-673
(2015),
arXiv:1404.4172
Recently a problem concerning the equivalence of joint measurability and
coexistence of quantum observables was solved [15]. In this paper we generalize
two known joint measurability results from sharp observables to the class of
extreme observables and study relationships between coexistence, joint
measurability, and post-processing of quantum observables when an extreme
observable is involved. We also discuss another notion of compatibility and
provide a counterexample separating this from the former notions.
Roope Uola, Tobias Moroder and Otfried Gühne
Joint measurability of generalized measurements implies classicality
Phys. Rev. Lett. 113,
160403
(2014),
arXiv:1407.2224
The fact that not all measurements can be carried out simultaneously is a
peculiar feature of quantum mechanics and responsible for many key phenomena in
the theory, such as complementarity or uncertainty relations. For the special
case of projective measurements quantum behavior can be characterized by the
commutator but for generalized measurements it is not easy to decide whether
two measurements can still be understood in classical terms or whether they
show already quantum features. We prove that generalized measurements which do
not fulfill the notion of joint measurability are nonclassical, as they can be
used for the task of quantum steering. This shows that the notion of joint
measurability is, among several definitions, the proper one to characterize
quantum behavior. Moreover, the equivalence allows to derive novel steering
inequalities from known results on joint measurability and new criteria for
joint measurability from known results on the steerability of states.