11:15 AM - 11:30 AM
▲ [18a-438-7] Experimental demonstration of controlled-NOT gate for time-bin qubits
Keywords:Quantum logic gate, Quantum information
The quantum logic gate for time-bin qubits will be useful for advanced quantum communication such as a quantum repeater based on quantum error correlation [1]. Recently, we demonstrated the controlled-phase (C-Phase) gate for time-bin qubits by using a two-input, two-output (2x2) optical switch which can work as a time-dependent beam splitter [2, 3]. Here, we demonstrate that the controlled-NOT (C-NOT) gate [4] for time-bin qubits can be realized with a 2x2 optical switch. Figure 1 (a) shows the setup. Here, we define the computational basis with different physical bases for control and target qubits. Alice and Bob prepare the computational ZZ basis as |t1> and |t2> for the control qubit and |+> and |-> for the target qubit, and XX basis as |+> and |-> for the control qubit and |t1> and |t2> for the target qubit, respectively [5], where |tx> is the photon in the temporal position of t1 and t2 and |+/->=1/Sqrt2(|t1> +/- |t2>). The input target qubits |+> or |-> are generated by launching the photon into a 1-bit delay interferometer, while the control qubits or are prepared by setting the temporal position of single photon pulses using an optical delay line, as shown in Fig. 1 (b) and (c), respectively. We pre-compensate the amplitudes of first temporal modes by adding one-third attenuation for both input states. As in the case of the C-Phase gate, we operate the 2x2 switch as a one-third beam splitter for second temporal mode, while the first temporal modes are passed through the switch. The output photons from the switch are sent into other two measurement interferometers to demonstrate the truth table of ZZ and XX basis as shown in the Fig. 1 (d) and (e). From the experimental result, the gate fidelity was estimated as 0.69 and 0.65, respectively. Thus, we successfully demonstrated a C-NOT gate for time-bin qubits.