We prove that all states (mixed or pure) of qubit–qutrit ( $$2\times 3$$ ) systems have entanglement-preserving unitary (EPU) equivalence to a compact subset true-generalized X (TGX) called EPU-minimal TGX which we give explicitly. Thus, for any spectrum–entanglement combination achievable by general states, there exists an state the same spectrum and entanglement. use I-concurrence measure ent...

The heavy fluxonium at zero external flux has a long-lived state when coupled capacitively to any other system. We analyze it by projecting all the relevant operators into qutrit subspace, as this configuration corresponds second excited level. This becomes bound-state in continuum (BIC) coupling occurs an extended system supporting of modes. In case without noise, we find BIC lifetimes that ca...

The problem of dephasing channel discrimination is addressed for finite-dimensional systems. In particular, the optimization with respect to input states without energy constraint solved analytically qubit, qutrit and ququart. Additionally, it shown that resorting side entanglement assisted strategy completely useless in this case.

The Ekert quantum key distribution protocol [1] uses pairs of entangled qubits and performs checks based on a Bell inequality to detect eavesdropping. The 3DEB protocol [5] uses instead pairs of entangled qutrits to achieve better noise resistance than the Ekert protocol. It performs checks based on a Bell inequality for qutrits named CHSH-3 and found in [10, 13]. In this paper, we present a ne...

We characterize control of a qutrit implemented in the lowest three energy levels capacitively shunted flux-biased superconducting circuit. Randomized benchmarking over Clifford group yields an average fidelity 98.89±0.05%. For selected subset group, we perform quantum process tomography and observe behavior repeated gate sequences. Each is generated using only two-state rotations via method ap...

We have recently shown that for the special case of a bipartite system with binary inputs and outputs there exist equalities in local theories which are violated by quantum theory. The amount of white noise tolerated by these equalities are twice that of inequalities. In this paper we will first introduce an inequality in bipartite qutrits systems which, if non-maximally entangled state is used...

We study the correlation structure of separable and classical states in 2× 2and 2× 3dimensional quantum systems with fixed spectra. Even for such simple systems the maximal correlation as measured by mutual information over the set of unitarily accessible separable states is highly non-trivial to compute; however for the 2× 2 case a particular class of spectra admits full analysis and allows us...