QUROPE Quantum Information Processing and Communication in Europe

We show that the time evolution of an open quantum system, described by a possibly time dependent Liouvillian, can be simulated by a unitary quantum circuit of a size scaling polynomially in the simulation time and the size of the system. An immediate consequence is that dissipative quantum computing is no more powerful than the unitary circuit model.

The QUIE2T-sponsored international conference on Quantum Information Processing and Communication (QIPC 2011) was held at ETH Zurich from September 5 - 9, 2011.

A detailed report on the conference is attached, see link  below.

Orbital physics plays an important in strongly-correlated electron systems, but coupling to other degrees of freedom often obscures its effects. A tunable system for exploring orbital physics alone is provided by ultracold spinless fermionic atoms in the p-band of an optical lattice.

We propose a method to probe dynamical spin correlations of strongly interacting systems in optical lattices. The scheme uses a light-matter quantum non-demolition interface to map consecutively a given non trivial magnetic observable of the strongly correlated system to the light. The quantum memory is essential to coherently store the previously mapped observable during a time scale comparable to the many-body dynamics. A final readout of the memory yields direct access to dynamical correlations.

Long range Rydberg blockade interactions have the potential for efficient implementation of quantum gates between multiple atoms. Here we present and analyze a protocol for implementation of a $k$-atom controlled NOT (C$_k$NOT) neutral atom gate. This gate can be implemented using sequential or simultaneous addressing of the control atoms which requires only $2k+3$ or 5 Rydberg $\pi$ pulses respectively. A detailed error analysis relevant for implementations based on alkali atom Rydberg states is provided which shows that gate errors less than 10% are possible for $k=35$.

We study the ability to control d-dimensional quantum systems (qudits) encoded in the hyperfine spin of alkali-metal atoms through the application of radio- and microwave-frequency magnetic fields in the presence of inhomogeneities in amplitude and detuning. Such a capability is essential to the design of robust pulses that mitigate the effects of experimental uncertainty and also for application to tomographic addressing of particular members of an extended ensemble. We study the problem of preparing an arbitrary state in the Hilbert space from an initial fiducial state.

We have realized a hybrid optomechanical system by coupling ultracold atoms to a micromechanical membrane. The atoms are trapped in an optical lattice, which is formed by retro-reflection of a laser beam from the membrane surface. In this setup, the lattice laser light mediates an optomechanical coupling between membrane vibrations and atomic center-of-mass motion. We observe both the effect of the membrane vibrations onto the atoms as well as the backaction of the atomic motion onto the membrane.

We measure the frequency dependence of the mechanical quality factor (Q) of SiN membrane oscillators and observe a resonant variation of Q by more than two orders of magnitude. The frequency of the fundamental mechanical mode is tuned reversibly by up to 40% through local heating with a laser. Several distinct resonances in Q are observed that can be explained by coupling to membrane frame modes. Away from the resonances, the background Q is independent of frequency and temperature in the measured range.

After the successful Industry Sessions held at the previous QIPC meetings in Barcelona’07 and Rome’09, the event at QIPC'11 again offered a platform for exchanges between academic researchers and industry leaders.

There were presentations by Dr. Bruno Michel, from IBM Research, Zürich, who talked about 'Computing after scaling: New computation paradigms', and Dr. Grégoire Ribordy, CEO of ID Quantique, who are celebrating their 10th anniversary this year. The title of his presentation was accordingly 'Commercializing QITechnology for 10 years'.

A dedicated channel on youtube to collect popular video clips on key scientific ideas explored within QIPC. This is sponsored by projects funded by FP6 and FP7 programs of the European Commission.

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