A Mølmer-Sørensen entangling gate is realized for pairs of trapped 111 Cd + ions using magneticfield insensitive "clock" states and an implementation offering reduced sensitivity to optical phase drifts. The gate is used to generate the complete set of four entangled states, which are reconstructed and evaluated with quantum-state tomography. An average target-state fidelity of 0.79 is achieved, limited by available laser power and technical noise. The tomographic reconstruction of entangled states demonstrates universal quantum control of two ion-qubits, which through multiplexing can provide a route to scalable architectures for trapped-ion quantum computing.PACS numbers: 03.67. Mn,03.65.Wj,03.65.Ud,32.80.Pj Entangled states such as the famous EPR-Bohm states [1,2] have long been of interest in the interpretation of quantum mechanics [3]; however, their generation has become a rapidly growing field with the recognition of entanglement as a powerful resource for quantum information processing [4]. Laser-addressed trapped ions with qubits embedded in long-lived internal hyperfine levels hold significant advantages for quantum information applications [5,6]. A critical issue is the robust generation of scalable entanglement. In the context of trapped ions this is reduced to the problem of two-qubit entanglement, as plausible multiplexing schemes have been proposed to create a scalable architecture for a quantum processor [7,8].Trapped-ion entangling gates mediated by phonons of the collective ion motion are susceptible to various forms of noise -qubit and motional decoherence, impure initial conditions, and technical issues associated with the optical Raman lasers driving the gate [5]. Robust schemes for gates based on spin-dependent forces have been proposed [9,10,11,12] and experimentally implemented [13,14] that, for example, relax the purity requirement on the initial motional state of the ions. Here we report the realization of one such entangling gate for pairs of trapped 111 Cd + ions that uses an advantageous implementation [15,16] of the Mølmer-Sørensen (MS) scheme [9,13]. The implementation reduces sensitivity to optical phase drifts through an appropriate Raman beam setup and reduces sensitivity to magnetic field fluctuations through the use of magnetic-field insensitive clock states [17].Quantum state tomography [18,19,20,21] is used to characterize the gate performance for the creation of all four entangled Bell-like states. Previous applications of quantum state tomography with ions include the reconstruction of non-classical states of motion [22,23,24] as well as entangled states of optical ion-qubits composed of electronic levels [20]. Here we present the first such implementation for hyperfine qubits, in the process demonstrating universal quantum control of two clock-state ionqubits.The MS gate for two trapped ions is based on optical Raman couplings to the first vibrational sidebands of the ions' collective motion, assumed along the z-axis. The ions are equally illuminated by a bichromatic R...