Discover and read the best of Twitter Threads about #ltqi

Most recents (24)

Now at #IWQNS, Kavan Modi from @MonashUni on Stochastic proceses and application to quantum networks
#LTQI
@MonashUni Kavan Modi: Classical stochastic processes can ofte be modelled by MArkov Chains, ore hidden markov chains, where the last n responses (n:= Markov order) are lumped together. #LTQI #IWQNS
@MonashUni Kavan Modi: What happens on quantum systems ? Like Biomolecule hit by a stream of laser pulses, or qubit modified by gates in presence of correlated environment. #LTQI #IWQNS
Read 7 tweets
Now at #IWQNS Zhang Zheshen form @UoA on Entanglement-Assisted Quantum Photonic Sensor Networks
#LTQI
@uoa Zhang Zheshen uses enatgled light to detect targets. His entaglement source, low brightness limit: # photon/mode N_s ≫ 1. Phase correlation |⟨â_s â_I⟩|≈√N_S ≫ N_S. #LTQI #IWQNS
@uoa Zheshen Zhang:
In an experiment with 14 dB loss, 75 dB Nouise background, quantum wins by 1 dB
arxiv:1411.5969 arxiv.org/abs/1411.5969 PRL 114 110506 doi.org/10.1103/PhysRe…
Ideal implementation would be 3 dB
Quantum bound is 6 dB (matched by explicit receiver)
#IWQNS #LTQI
Read 8 tweets
Now at #IWQNS, Kanupriya Sinha from @ArmyResearchLab and @JQInews on Tailoring fluctuation phenomena in nanophotonic systems: collective effects in Casimir-Polder forces & non-Markovian dynamics in atomic collective states
#LTQI
@ArmyResearchLab @JQInews Kanupriya Sinha; Casimir–Polder forces are important for integrated atom systems.
The interaction of a dipole at distance z of a mirror is U ∼ – ℏΓ₀/16(k₀z)³ : At z∼10 nm, U∼10 mK.
Where k₀ ← ω₀ (2 level split)
#LTQI #IWQNS
@ArmyResearchLab @JQInews Kanupriya Sinha looks at many ways to drive the interaction. #LTQI #IWQNS
Read 8 tweets
Now, at IWQNS, Sara Mouradian from @Berkeley_ions on Engineering Quantum Networks
#LTQI IWQNS
@Berkeley_ions Sara Mouradian did her PhD on NV centers, and now works on ion traps.
A single photon detected from two NV⁻ centers allows to prepare them in entangled state. Her NV's are at 10K. Current rate of entanglement is limite to much less than spin coherence time
#LTQI #IWQNS
@Berkeley_ions Sara Mouradian put her NVs in photonic crystal (diamond) cavities to improve entanglement rate. Her cavity has Q>14,000, but NVs are then close to surfaces, which broadens noise.
#LTQI #IWQNS
Read 5 tweets
Now at #IWQNS, Ashlesha Patil, Saikat’s student at @UoA speaks on Classical Simulation of Stabilizer Circuits
#LTQI #IWQNS
@uoa Ashlesha Patil demonstrates her Matlab tool, based on Gotoesman and Aaronson algorithm. For an arbitrary stabilizer state. If not a graph, proposes local unitaries converting it to a graph states, impements them (or others), and draw the relevant graph state
#LTQI #IWQS
@uoa Ashlesha Patil’s programme, also includes measurements: Pauli, Fusion gates (again including non-graph stabilizer state, with automatic translation to graph)
#LTQI #IWQNS
Read 4 tweets
Now at #IWQNS, Saikat Guha from @UoA on photonic quantum computing with discrete variable cluster states
#LTQI
@uoa Saikat Guha’s approach is on the “where is my photon ?” approach, based on progressive fusion of clusters. But
we do not understand the fundamental limits of corresponding measurement.
#LTQI #IWQNS
@uoa Saikat Guha: these measurement can be used to assemble small cluster states into greater lattices. Then percolation allows to expand this. He then gives several lattices with different thresholds, from .58 to .74 #LTQI #IWQNS
Read 5 tweets
Now at #IWQNS, Rafael N. Alexander from @UNM on quantum computing with continuous variable clusters
#LTQI
@UNM Rafael N. Alexander: Once you have a graph states allows you to do quantum computing with local operations, through measurement based quantum computation (MBQC). ∃ a sort of dictionnary translating circuits into graphical operations.
#IWQNS #LTQI
@UNM RAfael N. Alexander: 2 approahces for qauntum computing with bosonic modes:
1 = «Where is my photon ?», aka linear photonic computing
2 = «What is the state of my mode/oscillator ?» a.k.a. this talk
#LTQI #IWQNS
Read 7 tweets
Now ar #IWQNS Lincoln D. Carr @coschoolofmines on quantifying complexity in quantum phase transitions via mutual information complex networks
#LTQI
@coschoolofmines Lincoln D. Carr: In present quantum device (@dwavesys and analog devices) can already be described by networks difficult to simulate. Networks can be in the Hamiltonian, or arise spontaneously in the state. Here is about these spontaneous networks
#LTQI #IWQNS
Lincoln D. Carr‘s network arrise through quantum phase transition. The network is hidden in the adjacency matrix from the quantum state. The matrix is build from quantum mutual information between I_jk.
#LTQI #IWQNS
Read 7 tweets
Now at #IWQNS, @vparigi81 from @lkb_lab on Engineering non-Gaussian entangled complex photonic graph states .
#LTQI
@vparigi81 @lkb_lab .@vparigi81’s networks’ nodes are frequency/temporal modes of e.m. fields, made thorugh quantum frequency combs. That is merging optical frequency combs (OFC), with 10⁶ modes with quantum optics by pumping a parametric oscilaltorwith an OFC #LTQI #IWQNS
Read 9 tweets
Now at #IWQNS @SumeetKatri6
from @LSU on Robust NEtwork Architectures and topologies for entanglement distibution #LTQI #IWQNS
@LSU Sorry, wrong twitter handle: it’s @SumeetKhatri6
#LTQI #IWQNS
@LSU @SumeetKhatri6 .@SumeetKhatri6 : looks at 2D networks without quantum repeaters, using the multiplicity of paths to add robustness to losses and node failure.
#IWQNS #LTQI
Read 10 tweets
Now at #IWQNS, Don Towsley from @UMassAmherst on Entanglement routing and switching in quantum networks #LTQI
@UMassAmherst Don Towsley looks at repeaters/routers/switchs
With m links/link
Phase 1: link entanglement succeeds with p=1 – (1 — p₀)^m
Phase 2: splicing the links succeeds with probability q
#LTQI #IWQNS
@UMassAmherst Don Towsley study this in a grid network, with a single mode per link, one memory/mode, and a probability p to generate entanglement. #LTQI #IWQNS
Read 10 tweets
Now at #IWQNS, Prithwish Basu from U. Massachusetts on Routing and Scheduling in cClassiacal Networks #LTQI
Prithwish Bashu: Modern networks are not like internet in the 1970s. They’re no longer nice graphs, but now some king of hypergraphs with a mishmash of technologies.
#IWQNS #LTQI
Prithwish Basu: look at multi-hop routing in ad-hoc wirelss networks. Scheduling can be used to limit interference. In these networks, routing and scheduling cannot really be looking independently. #LTQI #IWQNS
Read 12 tweets
Now at #IWQNS, Roberta Zambrini, from @IFISC_mallorca on Quantum complex networks: introduction, Synchronization ans Noiseless subspaces #LTQI
@IFISC_mallorca Roberta Zambrini: classical complex networks are used to study the phenomenon of spontaneous synchronization. It has been recently generalized into the quantum regime
#LTQI #IWQNS
@IFISC_mallorca Roberta Zambini: The synchronization is induced by a dissipation. Two coupled squeezed harmonic oscillators need collective dissipation to become synchronized. (independent dissipation doesn’t lead to sync)
#IWQNS #LTQI
Read 8 tweets
Now at #IWQNS, Patrick Thiran from @EPFL presents an overview of classical an and complex networks. Mainly on classical networks, and on tools who might be applied to quantum networks.
#LTQI
@EPFL Patrick Thiran: Networks are complex. Layer abstraction helps to “divide and conquer”, but this abstraction comes at a cost, and sometimes it not worth it.
#LTQI #IWQNS
@EPFL Patrick Thiron: Case study1: wireless multi hop networks.
N→∞ nodes scatterred. We want full connectivity, study throughput scaling.
Layer 1. : Physical layer: adjust network for full connectivity
Layer 2: MAC connectivity
#LTQI #IWQNS
Read 10 tweets
Now at #QICA, Damian Markham from @ScienceSorbonne presents an Introduction to Quantum Networks
#LTQI
@ScienceSorbonne Damian Markham’s talk is actually steamed here facebook.com/watchparty/624…
Damian Markham recalls the advantages we expect from quantum information, in computation, simulation, communication, and sensing. #LTQI
Read 12 tweets
Seated for a talk by Mio Murao, form @UTokyo_News_en on Higher order quantum operations of blackbox unitaries and causal structure of the blackboxes. #LTQI
@UTokyo_News_en Mio Murao ([村尾 美緒) uses quantum computer to understand physics. What we can do do and what we cannot do are physics problems.
#LTQI
@UTokyo_News_en Mio Murao ([村尾 美緒) more specificely looks at maps of maps: The computer F takes as input a map f (e.g. given as a black box) and a quanutm state ρ and outputs F(f)(ρ).
Here we restrict ourseves to unitary f=U, and F(U)=V also unitary.
#LTQI
Read 12 tweets
Seated for a seminar on “Quantum Information Technology for Network”, by Qin Hai, from CAS Quantum Network Co., ltd, in Shanghai. This talk will essentially be focused on Chinese progress
#LTQI
Qin Hao: The chinese quantum satellite Micius has 3 mission. 1/ Act as a trusted quantum node, with QKD rate of 1 kbps (recently 400 kbps) ; 2/ Distribute entanglement between 1200km distant locations; 3/ Groud to satellite quantum state teloprtation
#LTQI
Qin Hao: The goal of the Chines Beijing–Shanghai 2000km QKD backbone is to have actual users. A next step (underway) is extend the backbone across China. And beyond, using satellites
#LTQI
Read 5 tweets
Seated for a talk by Mathieu Bozzio, on "Towards trusting your local Franprix's payment terminal..." a.k.a. “Money money money, must be funny, in a quantum world !”.

Joint work with Eleni Diamanti and myself, arXiv:1812.09256 arxiv.org/abs/1812.09256
#LTQI
Mathieu Bozzio: in the 1970s, Stephen Wiesner invented a quantum banknotes scheme, with security based on the no-cloning theorem.
Mint→Client→Bank

For quantum credit cards, there is classical communication between the Merchant and Bank:
Mint→Client→Merchant→Bank
#LTQI
Mathieu Bozzio’s approach : the attack cooresponds ti minimizing losses & error using convex optimization. To be practical, we use coherent states, with the following mapping
|0⟩→|α⟩⊗|vac⟩ ; |1⟩→|vac⟩⊗|α⟩
|±⟩→|α/√2⟩⊗|±α/√2⟩
|±i⟩→|α/√2⟩⊗|±iα/√2⟩
#LTQI
Read 6 tweets
Now seated for a seminar by Antoine Grospellier, from @inria_paris, on Constant overhead quantum fault-tolerance with quantum expander codes.

Associated paper: arXiv:1808.03821 arxiv.org/abs/1808.03821
#LTQI
@inria_paris Antoine Gropellier recalls the principle of quantum fault tolerance with concateneated Steane codes. Without correction, with error probability p, a circuit C, |C| gates and m qubits, Pr(wrong output)≤p|C|,
With code, 7m qubits, ≤c₀|C| gates, Pr(wrong)≤cp²|C|
#LTQI
@inria_paris Antoine Grospellier: with n iteration, 7ⁿm qubits, ≤c₀ⁿ|C| gates, Pr(Wrong)≤|C| (cp)^2ⁿ /c
This doubly exponenetial scaling of the error translates into a polylog(ε) scaling of the space overhead with the errors.
Ou main interest here is thii overhead
#LTQI
Read 11 tweets
Seated for a seminar by Francesco Arzani on his work with Nicolas Treps and Giulia Ferrini on
Polynomial approximation of non-Gaussian unitaries by counting one photon at a time (arXiv:/1703.06693 arxiv.org/abs/1703.06693 / PRA 95 052352 dx.doi.org/10.1103/PhysRe… )
#LTQI
Francesco Arzani: It’s difficult to define computation in a continuous variable (CV) set-up. People usually chose specific encoding of qubits. But Francesco (and myself!) finds encoding independent definitions more interesting.
#LTQI
Francesco Arzani: we are interested in the transformation exp(i H(q,p)).
A universal state should be bale to approximate any polynomial hamiltonian. arXiv:quant-ph/9810082 arxiv.org/abs/quant-ph/9… / PRL 82 1784 doi.org/10.1103/PhysRe… gave an example with quadratic gates + 1 cubic
Read 9 tweets
Seth Lloyd from @MIT is visiting us at LIP6 and presents his work with András Gilyén (from @QuSoftAmsterdam ) and @ewintang (from @UW) on Quantum-inspired low-rank stochastic regression with logarithmic dependence on the dimension arXiv:1811.04909 arxiv.org/abs/1811.04909
#LTQI
@MIT @QuSoftAmsterdam @ewintang @UW Seth Lloyd: presents the recommendation problem. For m users, n movies, a n×m matrix A encodes the movie preferences. The goal is to recommend movies a user likes, given their previous preferences.
A is assumed to be low rank (the rank is the effective number of genres).
#LTQI
@MIT @QuSoftAmsterdam @ewintang @UW Seth Lloyd: The @netflix way to solve this problem is through singular value decomposition of matrix A.

A=∑_l σ_l U^l V^l ^T
σ_l: singular values
U^l and V^l are left/right singular vectors
A V^l= σ_l U^l V^l
In short V^l^T b = p_l encodes weighted preference for genre l
#LTQI
Read 19 tweets
Seated for Niraj Kumar PhD defense, on Design, analysis and implementation of advanced quantum communication protocols
#LTQI
Niraj Kumar introduces the Simultaneous Message PAssing Model (SMP) (i.e. with a referee) to solve the Euclidean distance.
Classical complexity= Ω(√n)
Quantum Complexity=O(log n)
The quantum algorithm uses C-Swap to sample ½(1- |⟨x|y⟩|²

#LTQI
Niraj Kumar: Controlled SWAP are not realistic in the near term. @ixfoduap and Lutkehaus in 20114 found a way to map it to sequential coherent pulses interaction on a 50:50 beamsplitter and single photon detectors.
#LTQI
Read 14 tweets
Now at #JapanEUWorkshop, Shuntaro Takeda on A strategy for large-scale optical quantum computing #LTQI
Shuntaro Takeda: use a deterministic approach, a loop to increase scalability. Determinism is brought by continuous variable (CV) system, which need 5 gates to be universal: 3 linear, squeezing and cubic gate (the hard one) #LTQI #JapanEUWorkshop
Shuntaro Takeda: both discrete CNOT and CV cubit gates need χ⁽³⁾ and are therefore difficult, but the latter is at least deterministic.
#LTQI #JapanEUWorkshop
Read 7 tweets
Now at #JapanEUWorkshop , Anthony Laing on Photonic simulations of molecular quantum dynamics #LTQI
Anthony Laing essentially looks a photnic simulation of vibrational modes of molecules
Anthony Lang looks at selective dissociation with a single quantum of vibration NH₃→NH₂+H. These molecular transition can be manipulated through control of the wavepacket. #LTQI
Read 6 tweets

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