Demonstration of Density Matrix Exponentiation Using a Superconducting Quantum Processor

Autonomous stabilization with programmable stabilized state

“…We further demonstrate a parity switching capability between the Bell pairs with fast stabilization time constants (< 2 µs). We believe such freedom in choosing stabilized states will inspire generalization to autonomous stabilization of larger systems, large-scale many-body entanglement [3], remote entanglement [26], density matrix exponentiation [20,21], and new AQEC logical codewords in the future.…”

“…A generalized scheme that allows one to programmatically choose stabilized states from a large class of states per device will expand the toolbox for state preparation. For instance, the ability to choose an arbitrary stabilized state can be used for the implementation of density matrix exponentiation [20,21] by enabling an efficient reset of the input density matrix.…”

Experimental quantum teleportation of propagating microwaves

“…Our teleportation protocol allows us to violate the no-cloning limit over a wide range of input state parameters, corresponding to teleportation fidelities of F ≥ 0.69 for coherent states with the displacement photon number of n d ≤ 1.1 and the measurement gain G = 21 dB. Our experimental techniques rely exclusively on conventional aluminum-niobium superconducting parametric devices for generation and control of quantum microwave signals, which makes them fully compatible with other quantum superconducting circuits in terms of frequencies and fabrication technology, such as microwave quantum memory cells (30,31) or superconducting quantum processors (32). This natural technology match also avoids massive (∼10 −5 ) conversion losses of state-ofthe-art transducers between optical and microwave frequencies at the single photon level (33).…”

Parent Hamiltonian reconstruction via inverse quantum annealing

“…Such an approach does not involve the TDVP, providing a PH also when |𝜓(𝜆) crosses a phase transition. It could be implemented, for example, by mapping the Hamiltonian H (𝑡) to the state 𝜎(𝑡) ≡ (H (𝑡) + 𝐸 0 1)/Tr(H (𝑡) + 𝐸 0 1) and implementing the unitary evolution 𝑈 𝜋 (𝑡) through the density matrix exponentiation algorithm [44,45].…”